Chapter C: D. O'malley (1)

_Professor of Medical History, UCLA_

I

_Embryological Thought in Seventeenth Century England_

CHARLES W. BODEMER

To discuss embryological thought in seventeenth-century England is to discuss the main currents in embryological thought at a time when those currents were both numerous and shifting. Like every other period, the seventeenth century was one of transition. It was an era of explosive growth in scientific ideas and techniques, suffused with a creative urge engendered by new philosophical insights and the excitement of discovery. During the seventeenth century, the ideas relating to the generation and development of organisms were quite diverse, and there were seldom criteria other than enthusiasm or philosophical predilection to distinguish the fanciful from the feasible. Applying a well-known phrase from another time to seventeenth-century embryological theory, "It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness."[1]

Embryology underwent some very significant changes during the seventeenth century. At the beginning of the century, embryology was descriptive and clearly directed toward morphological goals; by the end of the century, a dynamic, more physiological attitude was apparent, and theories of development derived from an entirely different philosophic base. During this time, English investigators contributed much, some of ephemeral, some of lasting importance to the development of embryology. For this discussion, we will divide the seventeenth century into three overlapping, but generally distinct, periods; and, without pretence of presenting an exhaustive exposition, we will concentrate upon the concepts and directions of change characteristic of each period, with primary reference to those individuals who best reveal the character of seventeenth-century English embryology.

An understanding of the characteristics of embryological thought at the beginning of the seventeenth century may enhance appreciation of later developments. During the latter part of the sixteenth century, the study of embryology was, for obvious reasons, most often considered within the province of anatomy and obstetrics. From Bergengario da Capri to Jean Riolan the Younger, study of the fetus was recommended as an adjunct of these subjects, and it required investigation by direct observation, as decreed by the "restorers" of anatomy. Embryonic development was, however, also studied independently of other disciplines by a smaller group of individuals, and the study of chick development by Aldrovandus, Coiter, and Fabricius ab Aquapendente laid the basic groundwork of descriptive embryology. In either case, during the last half of the sixteenth century the attempt of the embryologist to break with the traditions of the past was overt, although consistently unsuccessful. When dealing with the fetus, the investigators of this period were, almost to a man, Galenists influenced to varying degrees by Hippocrates, Aristotle, and Avicenna. Each felt compelled to challenge the immediate authority, and yet their intellectual isolation from the past was incomplete, and their views on embryogeny corresponded with more often than they differed from those of the person they railed against.

Embryology emerged as a distinct scientific discipline during the last half of the sixteenth century and early years of the seventeenth century as a result of the aforementioned investigations of Aldrovandus, Coiter, and Fabricius. Concerned with description and depiction of the anatomy of the embryo, they established a period of macro-iconography in embryology. The macro-iconographic era was empirical and based upon first-hand observation; it was concerned more with the facts than with the theories of development. This empiricism existed in competition with a declining, richly vitalistic Aristotelian rationalism which had virtually eliminated empiricism during the scholastic period. However, the decline of this vitalistic rationalism coincided with the rise of a mechanistic rationalism which had its roots in ancient Greek atomistic theories of matter. The empiricism comprising the _leitmotif_ of the macro-iconographic movement then became blended with, or, more often, submerged within, the new variety of rationalism; hence, mechanistic rationalism, divorced entirely or virtually from empiricism, characterizes embryology during the first half of the seventeenth century. It is a particularly vigorous strain of seventeenth-century English embryological thought, well illustrated in the writings of that English man of affairs, Sir Kenelm Digby.

Digby, whose name, according to one biographer, "is almost synonymous with genius and eccentricity,"[2] could claim our attention not only as a scientist of talent, but also as a statesman, soldier, pirate, lover, and a Roman Catholic possessed of sufficient piety and naked courage to attempt the conversion of Oliver Cromwell. Like his father, who was hanged for participation in the Gunpowder Plot, Digby was a political creature, and during the Civil War he was imprisoned for several years. When freed, Digby left England to settle in France. Spending much time at the court of the Queen Dowager, who had been instrumental in securing his release, and exposed to the vigorous intellectual currents of Paris and Montpellier, Digby labored upon a treatise of greater scientific substance and merit than his more famous work on "the powder of sympathy." Published in 1644 under the title _Two Treatises, in the One of Which, The Nature of Bodies; in the Other, the Nature of Mans Soule; is Looked_ _into, in Way of Discovery of the Immortality of Reasonable Soules_, the book consists of a highly individual survey of the entire realms of metaphysics, physics, and biology.

Digby's cannons were aimed at scholasticism, which, despite "greatly exaggerated" reports, did not die with the Middle Ages. The spirit of scholasticism was alive in many quarters well into the seventeenth century, and although many scholars worked in pursuit of original knowledge, they did not always disturb the scholastic philosophic basis from which their work derived. For example, in his impressive _De formato foetu_, published in 1604, when Sir Kenelm Digby was one year old, Fabricius all too often submerges a substantial body of observations within a dense tangle of philosophical discussion. Thus, in the same treatise that contains the first illustrations and commendably accurate descriptions of the daily progress of the chick's development, Fabricius devotes an inordinate amount of space to tedious discussions of material and efficient causes in development, emphasizing thereby the supremacy of the logical framework to the observations. In 1620, Digby's last year of study at Oxford University, Fienus published a work, _De Formatrice Foetus_, designed to demonstrate that the human embryo receives the rational soul on the third day after conception and to discuss at length such subjects as the efficient cause of embryogeny and the proposition that the conformation of the fetus is a vital, not a natural, action. Various expressions of Aristotelian and scholastic biology were clearly abroad during the first half of the seventeenth century, and there is reason, then, for Digby's attack upon Aristotelian ideas of form and matter and of the persistence of "qualities" in physics and "faculties" in biology.

Expressing his disdain of word-spinning, Digby attempts to explain all phenomena by two "virtues" only, rarity and density working by local motion. In discussing embryonic development, Digby writes, "...our maine question shall be, Whether they be framed entirely at once; or successively, one part after another? And, if this later way, which part first?"[3] Toward this end, Digby makes some direct observations upon the development of the chick embryo, incubating the eggs so that the "creatures ... might be continually in our power to observe in them the course of nature every day and houre."[4] His description of chick development is of epigenetic bent:

...you may lay severall egges to hatch; and by breaking them at
severall ages you may distinctly observe every hourely mutation in
them, if you please. The first will bee, that on one side you shall
find a great resplendent clearnesse in the white. After a while, a
little spott of red matter like bload, will appeare in the middest
of that clearnesse fastened to the yolke: which will have a motion
of opening and shutting; so as sometimes you will see it, and
straight againe it will vanish from your sight; and indeede att the
first it is so litle, that you can not see it, but by the motion of
it; for att every pulse, as it openeth, you may see it, and
immediately againe, it shutteth in such sort, as it is not to be
discerned. From this red specke, after a while there will streame
out, a number of litle (almost imperceptible) red veines. Att the
end of some of which, in time there will be gathered together, a
knotte of matter which by litle and litle, will take the forme of a
head; and you will ere long beginne to discerne eyes and a beake in
it. All this while the first red spott of blood, groweth bigger and
solider; till att the length, it becometh a fleshy substance; and
by its figure, may easily be discerned to be the hart: which as yet
hath no other enclosure but the substance of the egge. But by litle
and litle the rest of the body of an animal is framed out of those
red veines which streame out all aboute from the hart. And in
processe of time, that body incloseth the hart within it by the
chest, which groweth over on both sides, and in the end meeteth,
and closeth it selfe fast together. After which this litle creature
soone filleth the shell, by converting into severall partes of it
selfe all the substance of the egge. And then growing weary of so
straight an habitation, it breaketh prison, and cometh out, a
perfectly formed chicken.[5]

Despite this observational effort, Digby's experience with the embryo is quite limited, and his theory of development relates more to his philosophical stance than to the facts of development. Indeed, the theory he propounds is not necessarily consistent. On the one hand, it posits a strictly mechanistic epigenesis, and on the other hand, it incorporates the notion of "specificall vertues drawne by the bloud in its iterated courses, by its circular motion, through all the severall partes of the parents body."[6] Digby rejects an internal agent, entelechy, or the Aristotelian formal and efficient causes. Similarly, he disposes of the idea that the embryonic parts derive from some part of each part of the parent's body or an assemblage of parts. This possibility is eliminated, he contends, by the occurrence of spontaneous generation. If a collection of parts was necessary, he asks, "how could vermine breed out of living bodies, or out of corruption?... How could froggs be ingendered in the ayre?"[7] Generation in plants and animals must, then, according to Digby, proceed from the action of an external agent, effecting the proper mingling of the rare and dense bodies with one another, upon a homogeneous substance and converting it into an increasingly heterogeneous substance. "Generation," he says,

is not made by aggregation of like partes to presupposed like ones:
nor by a specificall worker within; but by the compounding of a
seminary matter, with the juice which accreweth to it from without,
and with the streames of circumstant bodies; which by an ordinary
course of nature, are regularly imbibed in it by degrees; and which
att every degree do change it into a different thing.[8]

Digby argues that the animal is made of the juices that later nourish it, that the embryo is generated from superfluous nourishment coming from all parts of the parent body and containing "after some sort, the perfection of the whole living creature."[9] Then, through digestion and other degrees of heat and moisture, the superfluous nourishment becomes an homogeneous body, which is then changed by successive transformations into an animal.

Digby is frankly deterministic in his description of embryonic development:

Take a beane, or any other seede, and putt it into the earth, and
lett water fall upon it; can it then choose but that the beane must
swell? The beane swelling, can it choose but breake the skinne? The
skinne broken can it choose (by reason of the heate that is in it)
but push out more matter, and do that action which we may call
germinating.... Now if all this orderly succession of mutations be
necessarily made in a beane, by force of sundry circumstances and
externall accidents; why may it not be conceived that the like is
also done in sensible creatures; but in a more perfect manner....
Surely the progresse we have sett downe is much more reasonable,
then to conceive that in the meale of the beane, are contained in
litle, severall similar substances.... Or, that in the seede of the
male, there is already in act, the substance of flesh, of bone, of
sinewes, of veines, and the rest of those severall similar partes
which are found in the body of an animall; and that they are but
extended to their due magnitude, by the humidity drawne from the
mother, without receiving any substantiall mutation from what they
were originally in the seede. Lett us then confidently conclude,
that all generation is made of a fitting, but remote, homogeneall
compounded substance: upon which, outward Agents working in the due
course of nature, do change it into an other substance, quite
different from the first, and do make it lesse homogeneall then the
first was. And other circumstances and agents, do change this
second into a thirde; that thirde, into a fourth; and so onwardes,
by successive mutations (that still make every new thing become
lesse homogeneall, then the former was, according to the nature of
heate, mingling more and more different bodies together) untill
that substance be produced, which we consider in the periode of all
these mutations....[10]

Digby thus makes a good statement of epigenetic development. He attempts, without success, a physiochemical explanation of the mechanisms of development, finally admitting:

I persuade my selfe it appeareth evident enough, that to effect
this worke of generation, there needeth not be supposed a forming
vertue ... of an unknowne power and operation.... Yet, in
discourse, for conveniency and shortnesse of expression we shall
not quite banish that terme from all commerce with us; so that what
we meane by it, be rightly understood; which is, the complexe,
assemblement, or chayne of all the causes, that concurre to produce
this effect; as they are sett on foote, to this end by the great
Architect and Moderatour of them, God Almighty, whose instrument
Nature is.[11]

Digby's general theory thus represents a strange mixture of epigenesis and pangenesis, and is not entirely devoid of "virtues." It is, however, a bold attempt to explain embryonic development in terms commensurate with his time, and it embodies the same optimistic belief that the mechanism of embryogenesis lay accessible to man's reason and logical faculties that similarly led Descartes and Gassendi to comprehensive interpretations of embryonic development comprising a maximum of logic and minimum of observations.

The traditionalist reaction to the attack upon treasured and intellectually comfortable interpretations of development was not slow to set in. A year after the appearance of Digby's _Nature of Bodies_, Alexander Ross published a treatise with a title indicating its goals and content: _The Philosophicall Touch-Stone; or Observations upon Sir Kenelm Digbie's Discourses of the nature of Bodies, and of the reasonable Soule: In which his erroneous Paradoxes are refuted, the Truth, and Aristotelian Philosophy vindicated, the immortality of mans Soule briefly, but sufficiently proved_.[12] Ross supports the Galenist tradition that the liver, not, as Digby claimed, the heart, forms first in development. It can be no other way, he says, since the blood is the source of nourishment and the liver is necessary for formation of the blood. Furthermore, he contends, "the seed is no part of the ... aliment of the body ... the seed is the quintessence of the blood."[13] Ross is an epigeneticist, to be sure, but so was Aristotle, and Ross prefers to maintain the supremacy of logic and the concepts of the Aristotelian tradition as a guide to the interpretation of development.

In 1651, Nathaniel Highmore, a physician at Sherborne in Dorset, published _The History of Generation_, which, he informs us, is an answer to the opinions expressed by Digby in _The Nature of Bodies_. Highmore's book is an important one in the history of embryology, since it is the first treatment of embryogeny from the atomistic viewpoint and because it contains the first published observations based upon microscopic examination of the chick blastoderm. Admittedly, the drawings illustrating Highmore's observations upon generation are, to use a word often applied to modern art, "interesting," but they do derive from actual observations of developing plant and animal embryos. His observations on the developing chick embryo are quite full, complete, and exact, and he also records some interesting facts regarding development of plant seeds.

Highmore's theory of development appears to have emerged directly out of his observations of development. In this sense, his theory rests upon a more solid base than does the developmental theory of Digby. His theory is a mixture of vitalism and atomism, designed to eliminate the "fortune and chance"[14] resident in Digby's concept. "Generation," he says,

...is performed by parts selected from the generators, retaining
in them the substance, forms, properties, and operations of the
parts of the generators, from whence they were extracted: and this
Quintessence or Magistery is called the seed. By which the
Individuals of every Species are multiplied...

From this, All Creatures take their beginning; some laying up the like matter, for further procreation of the same Species.

In others, some diffus'd Atomes of this extract, shrinking themselves into some retired parts of the Matter; become as it were lost, in a wilderness of other confused seeds; and there sleep, till by a discerning corruption they are set at liberty, to execute their own functions. Hence it is, that so many swarms of living Creatures are from the corruption of others brought forth: From our own flesh, from other Animals, from Wood, nay, from everything putrified, these imprisoned seminal principles are muster'd forth, and oftentimes having obtained their freedom, by a kinde of revenge feed on their prison; and devour that which preserv'd them from being scatter'd.[15] Accounting thus for sexual and spontaneous generation, Highmore defines two types of seminal atoms in the seed--"Material Atomes, animated and directed by a spiritual form, proper to that species whose the seed is; and given to such matter at the creation to distinguish it from other matters, and to make it such a Creature as it is."[16] The seminal atoms come from all parts of the body, the spiritual atoms from the male, and the material atoms from the female. The atoms of Democritus are thus transmuted into the "substantial forms" and endowed either with the efficient cause of Aristotle or, permitted to remain material, with Aristotle's material cause. According to Highmore, the atoms are circulated in the blood, which is a "tincture extracted from those things we eat," and these various atoms retain their formal identity despite corruption. The testicles abstract some spiritual atoms belonging to each part and, "As the parts belonging to every particle of the Eye, the Ear, the Heart, the Liver, etc. which should in nutrition, have been added ... to every one of these parts, are compendiously, and exactly extracted from the blood, passing through the body of the Testicles." Being here "cohobated and reposited in a tenacious matter," the particles finally pass out of the testes.[17] A similar extraction of the female seed occurs in the ovaries. The female seed

...containing the same particles, but cruder and lesse digested,
from a cruder matter, by lesse perfect Organs, is left more
terrene, furnished with more material parts; which being united in
the womb, with the spiritual particles of the masculine seed;
everyone being rightly, according to his proper place, disposed and
ordered with the other; fixes and conjoynes those spiritual Atomes,
that they still afterwards remain in that posture they are placed
in.[18]

The theories of development promulgated by Digby and Highmore reveal the chief formulations of mechanistic rationalism, more or less free of empiricism, that were emerging as the vitalism of the sixteenth and seventeenth centuries waned. There was little new in these theories: both Digby's and Highmore's theories included different combinations of elements of ancient lineage. Digby's concept was essentially free of vitalistic coloring; akin to the embryological efforts of Descartes in its virtual independence from observations of the developing embryo, it was similarly vulnerable to Voltaire's criticism of Descartes, that he sought to interpret, rather than study, Nature. This criticism is not so applicable to Highmore, whose theory of development is more vitalistic than Digby's, and is more akin to the concepts developed by Gassendi than those of Descartes. Highmore had experience with the embryo itself, and his actual contribution as an observer of development, although hardly epochal, is worthy of note. But despite this empirical base, Highmore has final recourse to a hypothesis blending many ancient ideas and substituting the Aristotelian material and efficient causes for the "fortune and chance" he objected to in Digby's hypothesis. It was _not_ easy in the seventeenth century to avoid falling back upon some variety of cause or force.

In 1651, about two months before publication of Highmore's _History of Generation_, a work appeared which marks another period in seventeenth-century English embryology. William Harvey, _De Motu Cordis_ almost a quarter of a century behind him, now published _De Generatione Animalium_, the work he said was calculated "to throw still greater light upon natural philosophy."[19] This book is, perhaps, not as well known as Harvey's treatise demonstrating circulation of the blood, but it is an important work in the history of embryology and it occupies a prominent position in the body of English embryological literature.

In _De Generatione_, Harvey provides a thorough and quite accurate account of the development of the chick embryo, which, in particular, clarified that the chalazae, those twisted skeins of albumen at either end of the yolk, were not, as generally believed, the developing embryo, and he demonstrated that the cicatricula (blastoderm) was the point of origin of the embryo. The famous frontispiece of the treatise shows Zeus holding an egg, from which issue animals of various kinds. On the egg is written _Ex ovo omnia_, a legend since transmuted to the epigram _Omne vivum ex ovo_. The legend illustrates Harvey's principal theme, repeated constantly throughout the text, "that all animals were in some sort produced from eggs."[20]

If Harvey made no contribution beyond emphasizing the origin of animals from eggs, he would deserve a prominent place in the history of embryology. But the work is also significant in its espousal of epigenesis, and, supported as his argument was by observation and logic, it became the prime formulation of that concept of development during the seventeenth and eighteenth centuries. His statement of epigenetic development is clear:

In the egg ... there is no distinct part or prepared matter
present, from which the fetus is formed ... an animal which is
created by epigenesis attracts, prepares, elaborates, and makes use
of the material, all at the same time; the processes of formation
and growth are simultaneous ... all its parts are not fashioned
simultaneously, but emerge in their due succession and order ...
Those parts, I say, are not made similar by any successive union of
dissimilar and heterogeneous elements, but spring out of a similar
material through the process of generation, have their different
elements assigned to them by the same process, and are made
dissimilar ... all its parts are formed, nourished, and augmented
out of the same material.[21]

Actually, Harvey's exposition of epigenesis, albeit clear, is not totally impressive, since it is largely a reflection of Aristotle's influence. The main importance of Harvey's vigorous and cogent defense of epigenesis is that it provided some kind of counterbalance to the increasingly dominant preformationist interpretations of embryonic development.

Harvey did not break with Aristotelianism; on the contrary, he lent considerable authority to it. Unable to escape the past, he was not completely objective in his study of generation. Everywhere the pages of his book reveal his indebtedness to past authorities. Robert Willis, who provided the 1847 translation of _De Generatione_, expresses this well:

[Harvey] ... begins by putting himself in some sort of harness of
Aristotle, and taking the bit of Fabricius between his teeth; and
then, either assuming the ideas of the former as premises, or those
of the latter as topics of discussion or dissent, he labours on
endeavouring to find Nature in harmony with the Stagyrite, or at
variance with the professor of Padua--for, in spite of many
expressions of respect and deference for his old master, Harvey
evidently delights to find Fabricius in the wrong. Finally, so
possessed is he by scholastic ideas, that he winds up some of his
opinions upon animal reproduction by presenting them in the shape
of logical syllogisms.[22]

Even Harvey's concept of the egg reveals a strong Aristotelian bias. Actually, Harvey attained to his conclusion that all animals derive from eggs by assuming that

on the same grounds, and in the same manner and order in which a
chick is engendered and developed from an egg, is the embryo of
viviparous animals engendered from a pre-existing conception.
Generation in both is one and identical in kind: the origin of
either is from an egg, or at least something that by analogy is
held to be so. An egg is, as already said, a conception exposed
beyond the body of the parent, whence the embryo is produced; a
conception is an egg remaining within the body of the parent until
the foetus has acquired the requisite perfection; in everything
else they agree; they are both alike primordially vegetables,
potentially they are animals.[23]

The ovum, for Harvey, is in essence "the primordium vegetable or vegetative incipience, understanding by this a certain corporeal something having life in potentia; or a certain something existing _per se_, which is capable of changing into a vegetative form under the agency of an internal principle."[24] The ovum is for Harvey more a concept than an observed fact, and, as stated by one student of generation, "The _dictum ex ovo omnia_, whilst substantially true in the modern sense, is neither true nor false as employed by Harvey, since to him it has no definite or even intelligible meaning."[25]

Harvey's treatise on generation is clearly a product of his time. It advances embryology by its demonstration of certain facts of development, by its aggressive espousal of epigenesis and the origin of all animals from eggs, and by its dynamic approach stressing the temporal factors in development and the initial independent function of embryonic organs. However, the strong Aristotelian cast of Harvey's treatise encouraged continued discussion of long outdated questions in an outdated manner and, combined with his expressed disdain for "chymistry" and atomism, discouraged close cooperation between embryologists of different persuasions. It is perhaps easy to underestimate the impact and general importance of Harvey's work in view of these qualifications, and so it should be remarked that both positive and negative features of _De Generatione_ influenced profoundly subsequent embryological thought.

It will be recalled that the title of _The Philosophicall Touch-Stone_ identified Digby as the object of Alexander Ross's ire. In comparable manner, the latter's _Arcana Microcosmi_, published in 1652, declares its purpose to be "a refutation of Dr. Brown's Vulgar Errors, the Lord Bacon's Natural History, and Dr. Harvy's book _De Generatione_." Let us pause a brief moment in memory of a man so intrepid as to undertake the refutation of three of England's great intellects in one small volume, and then proceed to examine the embryological concepts of one of the trio, Sir Thomas Browne.

Browne's _Religio Medici_, composed as a private confession of faith around 1635, is known to all students of English literature, as is his later, splendid work on death and immortality, _Hydrotaphia, Urne-Buriall_. One of the greatest stylists of English prose, Browne was also a physician and a student of generation who deserves our attention as an early chemical embryologist pointing the way to a form of embryological investigation prominent in the last half of the seventeenth century.

Browne's embryological opinions are found particularly in _Pseudodoxia Epidemica_, _The Garden of Cyrus_, and in his unpublished _Miscellaneous Writings_. Browne, a well-read man, was educated at Oxford, Montpellier, Padua, and Leyden, and he was thoroughly imbued with the teaching of the prophets of the "new learning." This is evident throughout his writings, as witness his admonition to the reader of the _Christian Morals_:

Let thy Studies be free as thy Thoughts and Contemplations, but fly
not only upon the wings of Imagination; Joyn Sense unto Reason, and
Experiment unto Speculation, and so give life unto Embryon Truths,
and Verities yet in their Chaos.[26]

Browne greatly admired Harvey's work on generation, considering it "that excellent discourse ... So strongly erected upon the two great pillars of truth, experience and solid reason."[27] Browne carried out a variety of studies upon animals of all kinds, in them joining Sense unto Reason, and "Experiment unto Speculation." Thus in his studies of generation, he made observations and also performed certain simple chemical experiments. Noting that "Naturall bodyes doe variously discover themselves by congelation,"[28] Browne studied experimentally the chemical properties of those substances providing the raw material of development. He observed the effects of such agents as heat and cold, oil, vinegar, and saltpeter upon eggs of various animals, recording such facts as the following:

Of milk the whayish part, in eggs wee observe the white, will
totally freez, the yelk with the same degree of cold growe thick &
clammy like gumme of trees; butt the sperme or tredde hold its
former body, the white growing stiff that is nearest it.... Egges
seem to have their owne coagulum within themselves manifested in
the incrassations upon incubation.... Rotten egges will not bee
made hard by incubation or decoction, as being destitute of that
spiritt, or having the same vitiated.... How far the coagulating
principle operateth in generation is evident from eggs wch will
never incrassate without it. From the incrassation upon incubation
when heat diffuseth the coagulum, from the _chalaza_ or gallatine
wh. containeth 3 nodes, the head, heart, & liver.[29]

It cannot be said that Browne attained to any great generalizations regarding embryogeny on the basis of his rather naive experiments, but they are indicative of the effects of the "new learning" in one area of biology. Actually, Browne appears more comfortable in the search for patterns conforming to the quincunx, as in _The Garden of Cyrus_, and although he may well have been in search of something like the later Unity of Type, he uses his amassed details of scientific knowledge most effectively in support of nonscientific propositions. Thus, he uses the facts of embryonic development, alchemy, and insect metamorphosis as a part of his argument for the immortality of the human soul:

...for we live, move, have a being, and are subject to the actions
of the elements, and the malice of diseases in that other world,
the truest Microcosme, the wombe of our mother; for besides that
generall and common existence wee are conceived to hold in our
Chaos, and whilst wee sleepe within the bosome of our causes, wee
enjoy a being and life in three distinct worlds, wherin we receive
most manifest graduations: In that obscure world and wombe of our
mother, our time is short, computed by the Moone, yet longer than
the dayes of many creatures that behold the Sunne; our selves being
yet not without life, sense, and reason; though for the
manifestation of its actions it awaits the opportunity of objects;
and seemes to live there but in its roote and soule of vegetation;
entring afterwards upon the scene of the world, wee arise up and
become another creature, performing the reasonable actions of man,
and obscurely manifesting that part of Divinity in us, but not in
complement and perfection, till we have once more cast our
secondine, that is, this slough of flesh, and are delivered into
the last world, that ineffable place of Paul, that proper _ubi_ of
spirits. The smattering I have [in the knowledge] of the
Philosophers stone ... hath taught me a great deale of Divinity,
and instructed my beliefe, how the immortall spirit and
incorruptible substance of my soule may lye obscure, and sleepe a
while within this house of flesh. Those strange and mysticall
transmigrations that I have observed in Silkewormes, turn'd my
Philosophy into Divinity. There is in those workes of nature, which
seeme to puzzle reason, something Divine, and [that] hath more in
it then the eye of a common spectator doth discover.[30]

To affirm that Sir Thomas Browne was the founder of chemical embryology or, indeed, to contend that he made a great impress upon the progress of embryology is to humour our fancy. As Browne himself reminds us, "a good cause needs not to be patron'd by a passion."[31] His work and interpretations of generation are most important for our purposes as an indication of the rising mood of the times and an emerging awareness of the physiochemical analysis of biological systems. Although this mood and awareness coexist in Browne's writings with a continued reverence for some traditional attitudes, they mark a point of departure toward a variety of embryological thought prominent in England during the second half of the seventeenth century.

Browne did no more than analyze crudely the reaction of the egg to various physical and chemical agents. This static approach was later supplanted by a more dynamic one concerned primarily with the physicochemical aspects of embryonic development. This is first apparent in a report by Robert Boyle in the _Philosophical Transactions of the Royal Society_ in 1666 entitled, "A way of preserving birds taken out of the egge, and other small foetus's." Boyle, unlike Browne, exposed embryos of different ages to the action of "Spirit of Wine" or "Sal Armoniack," demonstrating thereby the chemical fixation of embryos as an aid to embryology. A year later, Walter Needham, a Cambridge physician who studied at Oxford in the active School of Physiological Research, which included such men as Christopher Wren and Thomas Willis, published a book reporting the first chemical experiments upon the developing mammalian embryo.[32] Needham's approach and goals are more dynamic than those of Browne, and he attempts to analyze various embryonic fluids by coagulation and distillation procedures. His experiments reveal, for example, that "coagulations" effected by different acids vary according to the fluid; thus, the addition of "alumina" to bovine amniotic fluid produced a few, fine precipitations, whereas the allantoic fluid was precipitated like urine. By such means Needham was able to demonstrate, however crudely, that there are considerable differences in the various fluids occurring within and around the fetus. Furthermore, it is with the results of chemical analyses that he supports his other arguments, such as his contention that the egg of elasmobranchs is not, as believed, composed of only one humour, but has separate white and yolk.

Needham's book contains many splendid observations, including an accurate description of the placenta and its vessels, the relationship of the various fetal membranes to the embryonic fluids, and rather complete directions for dissection of various mammals. These need not detain us, since the important aspect of Needham's work relevant to our purpose is his continuation of the chemical analysis of the developing embryo and its demonstration that, although Harvey might have despised the "chymists" and been contemptuous of the "mechanical, corpuscular philosophy," this system and approach was not to be denied.

Needham's book is dedicated to Robert Boyle, whose _Sceptical Chymist_ set the cadence for subsequent research based upon the "mechanical or corpuscularian" philosophy and quantitative procedures. It is appropriate for us, then, to terminate our discussion with a consideration of this current in English embryological thought.

John Mayow was the first to realize that "nitro-aerial" vapour, or oxygen, is essential to respiration of a living animal, and he was soon led to inquire "how it happens that the foetus can live though imprisoned in the straits of the womb and completely destitute of air."[33] As a consequence of this interest, the third of his _Tractatus Quinque medico-physici_, published in 1674, is devoted to the respiration of the fetus _in utero_. He shows truly remarkable insight when he concludes therein that

It is very probable that the spermatic portions of the uterus and
its carunculae are naturally suited for separating aerial particles
from arterial blood.

These observations premised, we maintain that the blood of the
embryo, conveyed by the umbilical arteries to the placenta or
uterine carunculae transports to the foetus not only nutritious
juice, but also a portion of the nitro-aerial particles: so that
the blood of the infant seems to be impregnated with nitro-aerial
particles by its circulation through the umbilical vessels in the
same manner as in the pulmonary vessels. Therefore, I think that
the placenta should no longer be called a uterine liver, but rather
a uterine lung.[34]

Although Mayow's attempted analysis of respiration of the chick embryo _in ovo_ is less than successful, his views on fetal respiration were soon accepted by many, and his tract stands as a great contribution to physiological embryology.

The studies of such individuals as John Standard reporting the weight of various parts of the hen's egg, e.g., the shell, the yolk, the white, reveal the wing of embryological investigation that was increasingly obsessed with quantification and the physicochemical analysis of the embryo and its vital functions. In this they were following the injunction of Boyle, who used the developing embryo as a vehicle in an attack upon the idea that mixed bodies are compounded of three principles, the obscurities of which operated to discourage quantification:

How will this hypothesis teach us, how a chick is formed in the
egg, or how the seminal principles of mint, pompions, and other
vegetables ... can fashion water into various plants, each of them
endowed with its peculiar and determinate shape, and with divers
specifick and discriminating qualities? How does this hypothesis
shew us, how much salt, how much sulphur, and how much mercury must
be taken to make a chick or a pompion? And if we know that, what
principle it is, that manages these ingredients, and contrives, for
instance, such liquors, as the white and yolk of an egg into such a
variety of textures, as is requisite to fashion the bones, veins,
arteries, nerves, tendons, feathers, blood, and other parts of a
chick? and not only to fashion each limb, but to connect them all
together, after that manner, that is most congruous to the
perfection of the animal, which is to consist of them?[35]

The emphasis upon quantification and the physicochemical analysis of vital processes was to continue into the eighteenth century and to contribute to the great stress upon precision in that period. It was not, however, destined to become immediately the main stream of embryological investigation. For even as the studies of Mayow were in progress, embryology was embarked upon a course leading to preformationism. By the end of the seventeenth century, the idea that the embryo was encased in miniature in either egg or sperm was elevated to a position of Doctrine, and thereafter there was little encouragement to quantitative study of development. Many embryological investigations were performed during the eighteenth century, but most relate to the controversy regarding epigenesis and preformationism as the true expression of embryonic development. Withal, the seventeenth-century embryologists, and particularly the embryologists of seventeenth-century England, had contributed much to the progress of the discipline. They had introduced new ideas, applied new techniques, and created new knowledge; they had effectively advanced the study of development beyond the stage of macro-iconography; they had freed the discipline from much of its traditional baggage of causes, virtues, and faculties. Various English embryologists had varying success with developmental theory, but as a group they had made great impact upon the development of embryology. In the course of their century, they had, in the words of one of them, "called tradition unto experiment."[36]

_Notes_

[1] Charles Dickens, _A Tale of Two Cities_, London, 1859, p. 1.

[2] Kenelm Digby, _Private Memoirs of Sir Kenelm Digby, Gentleman of the Bedchamber to King Charles the First_, London, 1827, Preface, p. i.

[3] Kenelm Digby, _Two Treatises, in the One of Which, The Nature of Bodies; in the Other, the Nature of Mans Soule; is Looked into_, Paris, 1644, p. 213.

[4] _Ibid._, p. 220.

[5] _Ibid._, pp. 220-221.

[6] _Ibid._, p. 222.

[7] _Ibid._, p. 215.

[8] _Ibid._, p. 219.

[9] _Ibid._, p. 213.

[10] _Ibid._, pp. 217-219.

[11] _Ibid._, p. 231.

[12] Alexander Ross, _The Philosphicall Touch-Stone; or Observations upon Sir Kenelm Digbie's Discourses of the nature of Bodies, and of the reasonable Soule_, London, 1645.

[13] Alexander Ross, _Arcana Microcosmi: or, The hid secrets of Man's Body disclosed ... In an anatomical duel between Aristotle and Galen concerning the parts thereof_, London, 1652, p. 87.

[14] Nathaniel Highmore, _The History of Generation, Examining the several Opinions of divers Authors, expecially that of Sir Kenelm Digby, in his Discourse of Bodies_, London, 1651, p. 4.

[15] _Ibid._, pp. 26-27.

[16] _Ibid._, pp. 27-28.

[17] _Ibid._, p. 45.

[18] _Ibid._, Pp. 90-91.

[19] William Harvey, _Opera omnia: a Collegio Medicorum Londinensi edita_, Londini, 1766, p. 136.

[20] William Harvey, _Anatomical Excercises on the Generation of Animals_, trans. Robert Willis, London, 1847, p. 462.

[21] _Ibid._, pp. 336-339.

[22] _Works of William Harvey_, trans. Robert Willis, London, 1847, pp. lxx-lxxi.

[23] Harvey, _op. cit._, pp. 462-463.

[24] _Ibid._, p. 457.

[25] F. J. Cole, _Early Theories of Sexual Generation_, Oxford, 1930, p. 140.

[26] Thomas Browne, _The Works_, ed. Geoffrey Keynes, Chicago, 1964, I, 261-262.

[27] _Ibid._, II, 265.

[28] _Ibid._, III, 442.

[29] _Ibid._, III, 442-452.

[30] _Ibid._, I, 50.

[31] _Ibid._, I, 14.

[32] Walter Needham, _Disquisitio anatomica de formato foetu_, London, 1667.

[33] John Mayow, "De Respiratione foetus in utero et ovo," in _Tractatus Quinque Medico-Physici_, Oxonii, 1674, p. 311.

[34] _Ibid._, pp. 319-320.

[35] Robert Boyle, _The Works_, London, 1772, I, 548-549.

[36] Browne, _op. cit._, II, 261.

II

_Robert Boyle as an Amateur Physician_

LESTER S. KING

Robert Boyle was not a physician. To be sure, he had engaged in some casual anatomical studies,[37] but he had not formally studied medicine and did not have a medical degree. Nevertheless, he engaged in what we would call medical practice as well as medical research and exerted a strong influence on the course of medicine during the latter seventeenth century, an influence prolonged well into the eighteenth. He lived during the period of exciting yet painful transition when medical theory and practice were undergoing a complete transformation towards what we may call the "early modern" form. The transition, naturally gradual, extended over three centuries, but I wish to examine only a very small fragment of this period, namely, the third quarter of the seventeenth century.

Boyle's first major work which dealt extensively with medical problems was the _Usefulness of Experimental Philosophy_. This work, although published in 1663, had been written in two parts, the first much earlier than the second. Fulton[38] indicates it had been drafted around 1650, while Hall[39] ascribes it to the period 1647-1648. This first part has relatively little to do with medicine; the references are few and rather incidental, and have significance only for the light they throw on "natural philosophy" and "natural religion." The second part, however, written apparently not too long before publication, has a great deal to do with medicine and constitutes one of the important medical documents of the century.

Deserving of mention is an earlier and minor work of Boyle, indeed, his first published writing, only recently identified. This work, apparently written in 1649, bore the title "An Invitation to a free and generous communication of Secrets and Receits in Physick," and appeared anonymously in 1655 as part of a volume entitled _Chymical, Medicinal and Chirurgical Addresses Made to Samuel Hartlib, Esquire_.[40] For our purposes, it is significant as emphasizing his early interest in medicine.

Boyle seems to have acquired most of his medical knowledge between, say, 1649 and 1662. It is worth recalling some of the trends and conflicts that formed the medical environment during this period. Among the major trends, first place, perhaps, must be given to Galenic doctrine, which had come under progressively severe attack. Molière, who lived from 1622 to 1673, showed in his comedies the popular reaction to a system which, although dominant, was clearly crumbling. The cracks in the edifice even the layman could readily see. Nevertheless, Galenism had its strong supporters. Riverius, who lived from 1589 to 1655, was a staunch Galenist. An edition of his basic and clinical works[41] was translated into English in 1657, and Latin editions continued to be published well into the eighteenth century.[42]

Galenism, of course, had to withstand the great new discoveries in anatomy and physiology made by Vesalius, Aselli, Sanctonius, Harvey, and others, not to mention the host of great investigators who were more strictly contemporaries of Boyle.

Galenism also faced the rivalry of chemistry. The so-called "antimony war" in the earlier part of the century marked an important assault on Galenism, and the letters of the arch-conservative Guy Patin (who died in 1672) help us appreciate this period.[43] However, even more important was the work of van Helmont, who developed and extended the doctrines of Paracelsus and represented a major force in seventeenth-century thought. Boyle was well acquainted with the writings of van Helmont, who, although his works fell into disrepute as the mechanical philosophy gradually took over, nevertheless in the middle of the seventeenth century was a highly significant figure. In 1662 there appeared the English translation of his _Oriatrike_,[44] while Latin editions continued to be published later in the century.

In this connection I might also mention the subject of "natural magic," which had considerable significance for medicine. The best-known name is, perhaps, Giovanni Battista della Porta (1545-1615), whose books[45] continued to be published, in Latin and English, during this period when Boyle was achieving maturity.

Profound developments, of course, arose from the new mechanics and physics and their metaphysical background, for which I need only mention the names of Descartes, who died in 1650, and Gassendi, who died in 1655. And then there was also the new methodological approach, that critical empiricism whose most vocal exponent was Francis Bacon, which led directly to the founding of the Royal Society in 1660 and its subsequent incorporation. These phases of seventeenth-century thought and activity I do not intend to take up.

In this turbulent riptide of intellectual currents, Robert Boyle, without formal medical education, performed many medical functions, as a sometime practitioner, consultant, and researcher. Repeatedly he speaks of the patients whom he treated, and repeatedly he refers to practitioners who consulted him, or to whom he gave advice. In addition, through his interest in chemistry, he became an important experimental as well as clinical pharmacologist, and his researches in physiology indicate great stature in this field. If we were to draw a present-day comparison, we might point to investigators who had both the M.D. and the Ph.D. degrees, who had both clinical and laboratory training, and who practiced medicine partly in the clinical wards, partly in the experimental laboratories. Boyle, of course, did not have either degree, but he did have a status as the leading virtuoso of his day.

The virtuoso has been the subject of a most extensive literature.[46] He aroused considerable contemporary hostility and satire and his overall significance for medical science is probably slight, with a few striking exceptions. Robert Boyle is one of the great exceptions.

First of all, the virtuoso was an amateur. In the literal sense the amateur loves the activities in which he engages, and in the figurative sense he remains independent of any Establishment. Not trained in any rigorous, prescribed discipline, he was not committed to any set doctrine. Furthermore, he was not restricted by the regulations which all Establishments employed to preserve their status, block opposition, and prevent competition. In many fields the Establishment took the form of a guild organization--in medicine, the Royal College of Physicians.[47]

Boyle was a wealthy and highly talented man who could pursue his own bent without needing to make concessions merely to earn a living. He remained quite independent of the cares which oppressed those less well endowed in worldly goods or native talent. Sometimes, of course, necessity can impose a discipline and rigor which ultimately may serve as a disguised benefit, but in the seventeenth century, when Boyle was active, the lack of systematic training and rigorous background seemed actually an advantage. Clinical chemistry and the broad areas which we can call experimental medicine had no tradition. Work in clinical chemistry, clinical pharmacology, and experimental physiology was essentially innovation. And since innovations are often made by those who are outside the Establishment and not bound by tradition, we need feel no surprise that the experimental approach could make great progress under the aegis of amateurs. Necessarily the work was rather unsystematic and undisciplined, but system and discipline could arise only when the new approach had already achieved some measure of success. Through the casual approach of amateurs this necessary foundation could be built.

Boyle, as a clinician, remained on excellent terms with medical practitioners. For one thing, he took great care not to compete with them. As stated,[48] he "was careful to decline the occasions of entrenching upon their profession." Physicians would consult him freely. As a chemist and experimental pharmacologist, he prepared various remedies. Some of these he tried out on patients himself, others he gave to practitioners who might use them. Boyle seems to have abundantly provided what we today call "curbstone consultations."

In no way bound by guild rules and conventions or by rigid educational standards, Boyle was free to learn from whatever sources appealed to him. Repeatedly he emphasized the importance of learning from experience, both his own and that of others, and by "others" he included not only physicians and learned gentlemen, but even the meanest of society, provided they had experience in treating disease. This experience need not be restricted to treatment of humans but should include animals as well. Thus, in speaking of even the "skilfullest physicians," he indicated that many of them "might, without disparagement to their profession, do it an useful piece of service, if they would be pleased to collect and digest all the approved experiments and practices of the farriers, graziers, butchers, and the like, which the ancients did not despise...; and ... which might serve to illustrate the _methodus medendi_."[49] He was quite critical of physicians who were too conservative even to examine the claims of the nonprofessionals, especially those who were relatively low in the social or intellectual scale. This casts an interesting sidelight on the snobbishness of the medical profession.

Boyle's willingness and ability to ignore the restrictions of an Establishment represent the full flowering of what I might call the Renaissance spirit--the drive to go outside accepted bounds, to explore, to _try_, to avoid commitment, and to investigate for oneself.

What internal and external factors permit a successful breakaway from tradition? Rebels there have always been, yet successful rebels are relatively infrequent. The late seventeenth century was a period of successful rebellion, and the virtuosi were one of the factors which contributed to the success. Robert Boyle played a significant part in introducing new methods into science and new science into medicine.

We must realize that Boyle was primarily a chemist and not a biologist. He thought in chemical terms, drawing his examples from physics and chemistry; he did not think in terms of the living creature or the organism, and as a mechanist he passed quite lightly over the concept or organismic behavior. His basic anti-Aristotelianism prevented his appreciating the biologically oriented thought of Aristotle. Instead, Boyle talked about the inorganic world, of water, of metals and elements, of physical properties. He ignored that inner drive which Spinoza called the _conatus_; or the _seeds_ of Paracelsus or van Helmont; or the persistence over a time course of any "essence" or "form." Since he dealt with phenomena relatively simple when compared with living phenomena, he could, for this very reason, make progress, up to a point. As a chemist, he could seek fairly specific and precise correlations of various concrete environmental factors, and then assume that living beings behaved as did the inorganic objects which he investigated. However, he always excepted the soul of man, as outside his investigations.

But while Boyle was a skillful chemist, judged by the standards of his time, we cannot call him a skillful medical investigator. This represents, however, the fault of the era in which he lived rather than any fault peculiar to him. Boyle's medical studies fall into at least two categories. These were the purely physiological experiments, such as those on respiration or on blood, and the more clinical experiments, concerned with pharmaceuticals, clinical pharmacology, and clinical medicine. The purely physiological experiments have great merit and were profoundly influential in shaping modern physiology. The clinical experiments throw great light on the development of critical judgment in medical history, and the relations of judgment and faith.