Chapter I: Monas

Vermis inconspicuus, simplissimus, pellucidus, punctiformis. An invisible,[122] pellucid, simple, punctiform worm.

[122] By invisible, we only mean that they are too small to be
discerned by the naked eye.

1. MONAS TERMO. M. gelatinosa. Gelatinous mona.

Animalcules semblable a des points. Spallanzani Opusc. Phys. I. Bullæ continuo motu. Bonanni Obs. p. 174.

Among the various animalcula which are discovered by the microscope, this is the most minute, and the most simple; a small jelly-like point, eluding the powers of the compound microscope, and being but imperfectly seen by the single; these, and some others of the mona kind, are so delicate and slender, that it is no wonder they often escape the sight of many who have examined infusions with attention; in a full light they totally disappear, their thin and transparent forms blending as it were with the water in which they swim.

Small drops of infused water are often so full of these, that it is not easy to discover the least empty space, so that the water itself appears changed into another substance less transparent, but consisting of innumerable globular points, thick sown together; which, though full of life, seem only a kind of inflated bladders. In this a motion may be perceived, something similar to that which is observed when the sun’s rays shine on the water, the animalcula being violently agitated, or in a commotion like unto a hive of bees. They are very common in ditch water, and in almost all infusions, both of animal and vegetable substances.

2. MONAS ATOMUS. M. albida puncto, variabili instructa, Plate XXV. Fig. 1. White mona, with a variable point.

This animalculum appears as a white point, which, when it is highly magnified, is somewhat of an egg-shape; the smaller end is generally marked with a black point; the situation of this is sometimes varied, and found at the other end of the animalculum: sometimes two black points are to be seen crossing the middle of the body. It was found in sea water that had been kept the whole winter; it was not, however, very fetid; there were no other animalcula in the same water.

3. MONAS PUNCTUM. M. nigra. A black mona.

A very minute point, solid, opake and black, round and long. They are dispersed in the infusion, and move with a slow wavering motion; were found in a fetid infusion of pears.

4. MONAS OCELLUS. M. hyalina puncto centrali notata. Transparent like talc, with a point in the middle.

The margin black, and a black point in the middle; it moves irregularly, is found in ditches covered with conferva, and frequently with the cyclidium milium, see No. 84.

5. MONAS LENS. M. hyalina. Transparent mona of the appearance of talc.

This is among the number of the smaller animalcula, nearly of a round figure, and so pellucid, that it is not possible to discover the least vestige of intestines. Though they may often be seen separate, yet they are more generally collected together, forming a kind of vesicular or membranaceous mass. Contrary to the custom of other animalcula, they seek the edges of the evaporating water, the consequence of which is almost immediate death. When the water is nearly evaporated, a few dark shades are perceived, probably occasioned by the wrinkling of the body. A slow tremulous motion, confined to one spot, may be perceived at intervals; this in a little time becomes more lively, and soon pervades the whole drop. Its motions are in general very quick: two united together may sometimes be seen swimming among the rest; while in this situation, they have been mistaken by some writers for a different species, whereas it is the same generating another by division. It is to be found in all water, though but seldom in that which is pure; they are in great plenty in the summer in ditch water, also in infusions of animal or vegetable substances, made either of fresh or salt water, myriads being contained in a drop; numbers of various sizes are to be found in the filth of the teeth.[123]

[123] The circumstance of animalcula being found in the teeth is
mentioned with confidence by various authors; some doubts may,
however, still remain of the fact. Mr. Willughby detected a woman, who
pretended to take worms out of the teeth with a quill, having forced
the quill, from her just as she was putting it into his mouth, and
found small worms in it; see Birch’s History of the Royal Society,
vol. iv. p. 387. I am inclined to think that the accounts usually met
with in authors have no better foundation. It has also repeatedly
happened, that ingenious men, from their anxiety for discovery, have
imagined that objects have appeared to their view, which, having
related as facts, themselves or others have afterwards found to be
nothing more than a deceptio visus; and thus they have been, at least
for a time, the unintentional promulgators of error; considerable
caution is therefore necessary on these occasions, see p. 132, 133.

Some authors, in support of a favourite system, have made bold
assertions on the subject of animalcula; the small-pox, the measles,
the epilepsy, &c. have been attributed to them: Langius reduces all
diseases in general to the same principle. A writer at Paris, who
assumed the title of an English physician, has proceeded still
farther; he not only accounts for all diseases, but for the operation
of all medicines, from the hypothesis of animalcula. He has peculiar
animals for every disorder; scorbutic animalcula, podagrical
animalcula, variolous animalcula, &c. all at his service. Journ. des
Scav. tom. lxxxvii. p. 535, &c.

It is not at all surprising that the wonderful discoveries relating to
animalcula should have been applied, however improperly, to support
the most whimsical and chymerical systems. Most of the discoveries in
natural philosophy have been subjected to similar abuses, and laid the
foundation for the warm imaginations of some men to fabricate
visionary theories; these have been of great prejudice to real
science, the primary object and ultimate reward of which is the
acquisition of truth. EDIT.

The animalcula of this, and the first species are so numerous as to exceed all calculation, though they are contained in a very confined space.

6. MONAS MICA. M. circulo notata. Mona, marked with a circle.

This lucid little point may be discovered with the third lens of the common single microscope; when the magnifying power is increased, it appears either of an oval or spherical figure, for it assumes each of these at pleasure. It is transparent, and has a small ellipse inscribed as it were within its circumference; this ellipse is moveable, being sometimes in the middle, sometimes a little towards the fore-part, at others, nearer the hind-part. There is a considerable variety in its motions; it often turns round for a long time in the same place; an appearance like two kidneys may sometimes be perceived in the middle of the body, and the animalculum is beautifully encompassed with a kind of halo, arising most probably from invisible and vibrating fibrillæ. They are to be found in the purest waters.

7. MONAS TRANQUILLA. M. ovata, hyalina, margine nigro. Egg-shaped, transparent mona, with a black margin.

These animated points seem to be nearly fixed to one spot, where they have a fluctuating or reeling motion. They are frequently surrounded with a halo, and differ in their figure, being sometimes rather spherical, at others quadrangular. The black margin is not always to be found, and sometimes one would almost be tempted to think it had a tail. They are found in urine which has been kept for a time. The urine is covered, after it has remained in the vessel, with a dark-coloured pellicle or film, in which these animals live: although the urine was preserved for several months, no new animalcula were observed therein. It has been already shewn, that a drop of urine is in general fatal to other animalcula, yet we find in this instance, that there are animated beings of a peculiar kind, appropriated to, and living in it.

8. MONAS LAMELLULA. M. hyalina compressa. Flat transparent mona.

This is mostly found in salt water. It is of a whitish colour, more than twice as long as it is broad, transparent, with a dark margin, the motion vacillatory; it often appears as if double.

9. MONAS PULVISCULUS. M. hyalina, margini virente. Transparent mona, with a green margin.

Little spherical pellucid grains of different sizes, the circumference green, a green bent line passes through the middle of some, probably indicating that they are near separating or dividing into two distinct animalcula; sometimes three or four, at others, six, seven, or even more, are collected together. They rove about with a wavering motion; and are mostly found in the month of March in marshy grounds.

10. MONAS UVA. M. hyalina gregaria. Transparent gregarious mona.

It is not easy to decide on the nature of these little assemblages of corpuscles, which sometimes consist of four, at others of five, and frequently of many more: the corpuscles are of different sizes, according to the number assembled in one group. When collected in a heap, the only motion they have is a kind of revolution or rotatory one. The smaller particles separate from the larger, often dividing into as many portions as there are constituent particles in the group; when separated, they revolve with incredible swiftness. To try whether this was a group of animalcula collected together by chance, or whether this was their natural state, the following experiment was made. A single corpuscle was taken the moment it was separated from the heap, and placed in a glass by itself; it soon increased in size, and when it had attained nearly the same bulk as the group from which it was separated, the surface began to assume a wrinkled appearance, which gradually changed till it became exactly similar to the parent group. This new-formed group was again decomposed, like the preceding one, and in a little time the separated particles became as large as that from which they proceeded. It is found in a variety of infusions.