Chapter XVI: Section III: NEMATODA (Round Worms) (4)

The guinea-worm having been known from the earliest times, it is not surprising that its true nature long remained a mystery. Any one who has read Küchenmeister’s elaborate narrative of the historical significance of the Dracunculus will hardly have failed to arrive at the conclusion that Moses was probably the earliest writer on the endemic disorder which is occasioned by this parasite. There can be no doubt that the “fiery serpents” which afflicted the children of Israel during their stay in the neighbourhood of the Red Sea were neither more nor less than examples of our Dracunculus. It is further evident that Plutarch spoke of Dracunculi, when in the eighth book of his ‘Symposiacon,’ he quotes Agatharchidas as stating that the people taken ill on the Red Sea suffered from many strange and unheard-of attacks, amongst other worms, from “little snakes, which came out upon them, gnawed away their legs and arms, and when touched retracted, coiled themselves up in the muscles, and there gave rise to the most insupportable pains.” In order to render the passage more readable, it will be seen that I have slightly altered the original version (‘Parasites,’ s. 305).

The guinea-worm may be described as a nematode measuring from one to six feet in length, having a thickness of 1/10th of an inch. The body is uniformly cylindrical, terminating below in a more or less curved and mucronately pointed tail. The head is flatly convex or truncate, having a central, simple mouth, which is surrounded by four equi-distantly and cruciately disposed papillæ. The mode of reproduction is viviparous, the body enclosing a prodigious number of hatched embryos, which, by distension of the uterine ducts, almost entirely obliterate the somatic cavity. Notwithstanding the statements of Owen to the contrary, the male Dracunculus is at present altogether unknown.

The guinea-worm possesses a comparatively limited geographical range, for not only is it proper to the tropical regions, but within intertropical limits it is almost exclusively confined to certain districts in Asia and Africa. Thus, according to Künsenmuller, as quoted by Busk, it occurs endemically in Arabia Petræa, on the borders of the Persian Gulf and Caspian Sea, on the banks of the Ganges, in Upper Egypt, Abyssinia, and the coast of Guinea. “In America the guinea-worm is unknown, except in persons who have had communication with Africa or other parts where it is indigenous. The island of Curaçoa is the only locality in the New World which offers an apparent exception to this fact, and it would be highly desirable to ascertain the real state of the case in this instance.” The observations of Chisholm showed that the Dracunculus is really prevalent in several of the West Indian islands, especially in Grenada, and the still later investigations of Dr Da Silva Lima point to its former prevalence in Brazil. Now, the worm is rarely seen at Bahia. Mr Busk said:--“Though endemic only in the above-mentioned parts of the world, it would yet appear that all races of mankind are obnoxious to the attacks of the _Filaria_ when exposed to what may be called the contagion; that is, when placed in circumstances under which it might be supposed a contagious _seminium_ could be conveyed to them.” Mr Busk also added:--“I have known many instances tending to prove that, in order that a European should become infected with the guinea-worm on the coast of Africa, it is not necessary that he should have been on shore at all. It has been quite sufficient for him to have exposed the bare surface of some parts of his person to the water in the native canoes alongside, or, it may be, to the discharge from the sores of those laboring under the disease. This mode of its introduction accounts for the frequency with which the legs and feet are attacked by the parasite, in preference to other parts of the body, as it will always, I believe, be found that the men who have become so affected have been in the habit of going about with bare feet, as is common among sailors in warm latitudes. That the contagious material is conveyed in water is also further indicated by the well-known fact that in India, where it is the custom of the natives to carry water in skins on their backs, the worm makes its appearance on the back and shoulders and upper part of the body.” These views were published by Busk in 1846, and I am free to confess that--confirmed as they appeared to be by subsequent and independent testimony--they completely dominated my conceptions as to the mode of ingress of the young parasites within the human bearer. Thus, those of our Indian troops which were most exposed during the rainy season, subsequently exhibited evidence of having been invaded by the Dracunculus. As, moreover, the period of incubation of the entozoon commonly extends from twelve to fifteen months, it necessarily happened that the disease often showed itself in localities far distant from the spot where the troops originally contracted the disorder. The statement that the period of incubation of the worm is not less than a year, is probably incorrect, since Carter mentions that in a school of fifty boys bathing in a certain pond at Bombay--the sediment of which swarmed with microscopic tank-worms (_Urobales palustris_, Carter)--twenty-one were attacked with Dracunculus during the year, whilst the boys of other schools, bathing elsewhere, remained, with few exceptions, uninfected. This is a remarkable occurrence, and it points to the possibility of the young Dracunculi being confined to particular pools. That they should, whether occupying the bodies of intermediary bearers or not, be more abundant in some waters than others, is just what might be expected, since such a distribution is in harmony with a recognised law affecting the abundance or limitation of species in particular localities. Much, indeed, has been written respecting the nature of the soil and geological formations occurring in the Indian worm-districts, but the speculative views enunciated on this point are little worthy of credit. Those who desire information on this head should at all events consult the valuable writings of Smyttan, Greenhow, Bird, Forbes, Chisholm, and Aitken, who, apart from the question at issue, supply abundance of practical information.

Into the anatomy of the adult Dracunculus I do not enter, but I may remark in passing, that the structure of the worm has been exhaustively treated of by Busk and Bastian. A _résumé_ of their views is given in my introductory treatise. Carter and Leuckart have also added important details. As regards the structure and development of the young worms, I have to observe that the discovery of the viviparous mode of reproduction in Dracunculus is due to Jacobson. Nearly a quarter of a century ago I recognised the fact that the uterine organs of the adult worm almost completely filled up the perivisceral cavity, and that they were crowded with microscopic worms. Referring to this “find,” the late Sir George Ballingall, of Edinburgh, in his well-known work on ‘Military Surgery,’ recorded the circumstance in the following terms:--“The Assistant Conservator of the Anatomical Museum in our University has detected _in the oviduct_ of an adult specimen from my collection myriads of minute and perfectly-developed (embryonic) Dracunculi. They can be very well seen with an half-inch object-glass, but their structure is best exhibited if the magnifying power be increased to two hundred and fifty diameters linear.” As already stated in my introductory treatise, these observations were made during the winter of 1853-54. In July, 1854, M. Robin made a similar statement after examining a fresh _Dracunculus_ which had been extracted from the leg of a man by M. Malgaigne. Robin, not unsuitably, compared the worm to a double tube, one tubular sheath, as it were, enclosing the other. “The second tube,” he distinctly affirms, “_is the oviduct, or, rather, that part which represents the uterus_. The young still remaining in the uterus were nearly all coiled, sometimes with the tail sallying outwards, at others rolled like the rest of the body.” I have thought it only due to Robin and myself to show that from the first we were perfectly well acquainted with the fact of the “great development of the genital tube and of its close adherence to the parietes of the body.” To be sure, many discrepancies occurred in our writings, and in those of Busk and Carter. It was Bastian’s skill and good fortune to correct these errors. Thus, most of us agreed in recognising a slightly trilobed or tripapillated mouth; but Carter failed to demonstrate the existence of these tubercles, and spoke of the oral aperture as being simple and “punctiform.” The body throughout its three upper fourths appeared to me to be cylindrical, but Robin found that it was flattened. It is finely striated transversely, except at the part where it contracts to form the slender, pointed tail. According to Carter, Robin, and Davaine, the young attain a length of about 1/33 of an inch, but Bastian gives it as about 1/42″. In thickness, Carter gives the approximative diameter as 1/633″, Robin makes it 1/990″ to 1/1320″, whilst Bastian gives their breadth at 1/1428″, and Davaine at 1/2500″. I estimated their greatest length and breadth to be 1/30″ by 1/1000″. Robin and myself thought we recognised a distinct, rounded, anal orifice; and whilst Busk, on the one hand, saw nothing which in the slightest degree indicated the presence of an anal opening, Carter, on the other hand, described the structure which we called the anus as a gland, at the same time placing the alimentary outlet on one side and a little above it. According to Bastian, “the intestinal tube is about 1/87″ in length, and appears to consist of a simple canal of varying calibre, pursuing a nearly straight course, and terminating exactly at about the middle, in length, of the worm.” Like Robin, Bastian recognised œsophageal and stomachal divisions, and in a few examples he observed the cæcal or terminal portion of the intestine to be partially reflected upon itself. In regard to the circular opening which Robin and myself described as the anus, Bastian says there is a rounded body, “about 1/2200″ in diameter, with a dark or light spot in the centre, according to the varying focal distance, and which seems to represent a central aperture. Sometimes, above this, traces of two or three large cells may be recognised, whilst behind nothing definite can be made out, save that the cavity of the body is visible for about 1/400″. In other specimens of the young worm the central body and spot are wanting, but, in its stead, two lateral sacculi are met with, about 1/3300″ in diameter, that communicate with the exterior by a minute channel through the integuments, which can sometimes be distinctly recognised. At other times the channel is obscured by protrusion, which appears to have taken place through it, of a minute bilobed papilla, projecting 1/10,000″ from the side of the body. When the projections are seen, the sacculi are indistinct.”

As Bastian found the young in all stages of development from the germ condition 1/5000″ in diameter up to the perfect embryo, and as, moreover, he, like the rest of us, could detect no sexual orifice in the adult Dracunculus, he was led to express his belief that the young were produced agamogenetically. He went so far as to call the germs _pseudova_. It was with great reluctance that I dissented from the views of so gifted an observer as Bastian; nevertheless, later researches have shown that I was justified in not hastily concurring in the theory of a non-sexual mode of reproduction for Dracunculus.

Among the many advances of modern helminthology, the discovery of the true source of the guinea-worm is not the least important. To the late M. Fedschenko (the lamented and accomplished Russian traveller, who lost his life in a snowstorm on the Alps), science stands indebted for this memorable advance. Fedschenko showed that the embryos of Dracunculi, after quitting the human host, succeed in effecting an entry into the bodies of entomostracous crustaceans belonging to the genus Cyclops. Within these intermediary bearers, after twelve hours’ sojourn, the embryos undergo a change of skin, attended with subsequent growth. Here they remain to complete their larval development, which takes place within a period of five weeks, or, as Fedschenko himself told me, one month and six days. At length, as perfected larvæ, they are, together with their crustacean hosts, transmitted to the stomach of the ultimate or human bearer. It is probable that sexual maturity is next acquired within the human stomach, copulation following. After this, the females migrate to the situations in which they are found beneath the skin of the human bearer, whilst the males perish and pass out with the fæces. Thus much I gathered from M. Fedschenko himself when he visited this country, and I possess a sketch of the larvæ made by him at the time (October 23rd, 1873). One of the figures represents a larva which has undergone ecdysis, the long and narrow embryonic tail being supplanted by one which is blunt and forked at the tip. The somatic contents of the embryo have at the same time differentiated into a complete intestinal tube, and a constriction marks the junction of the œsophagus with the stomach. There is also internally an oval-shaped mass of cells near the centre of the body. These represent the commencement of the reproductive organs.

What I had gathered from Fedschenko in conversation thus epitomises that which has since been much more fully stated by Leuckart; and it is only fair to add that the Russian traveller was led up to his discovery by the previous investigations of Leuckart respecting the young of Cucullanus. The Leipsic helminthologist had, indeed, specially instructed Fedschenko as to the probable source of Dracunculus.

It is often thus that science makes its clear advances, since a master-mind is needed to set others on the right track. The embryos of Cucullanus and Dracunculus bear a close resemblance to each other, and the similarity of the types is continued on, though not in the same degree, in the next stage of larval growth, after ecdysis. The higher larvæ of both have their tails trifurcate at the tip, the head of the Dracunculus-larva being distinguished by the presence of a pair of papillæ. In the case of Cucullanus the embryos are, according to Leuckart, passively transferred to the stomach of Cyclops by the mouth; but in the case of Dracunculus, Fedschenko saw the embryo in the act of perforating the bodies of the little crustacea at the ventral surface, where the segments are bound together by a thin and easily penetrated connecting membrane. The larvæ then proceed to coil themselves within the limbs, as many as six or even a dozen of the parasites being occasionally found within the body of a single crustacean host. When they have reached full larval growth they measure about 1/25″ in length. Of course, after attaining this stage, it is a matter of conjecture as to the precise way in which their final destiny is accomplished. Fedschenko fed dogs and cats with the infected crustacea, but failed to rear Dracunculi in these animals. Clearly, these carnivora were unsuitable hosts. Could Fedschenko have experimented on man the result would probably have been very different. Arguing from what happens in the case of Cucullanus amongst fishes, and Trichina in man, there can be little doubt that all the further and final changes undergone by the larvæ are accomplished within the human host. These changes are usually, if not invariably, consequent upon a direct transference of the infested entomostraca along with water used as drink. Thus, it must at once be evident that the simple sanitary precaution of filtering water before use is amply sufficient to ensure the prevention of attacks of dracontiasis or the guinea-worm disease. The theosophical remedy of Moses against this invasion by fiery serpents, as the worms were called in his time, and the modern prophylactic measures dictated alike by science and common sense, thus stand in striking contrast the one to the other. In the nature of things it must ever remain that unreason and reason will select diametrically opposite methods of action, equally, no doubt, with the good intention of bringing about beneficial results.

From what has now been advanced, it will be seen that as regards the mode of infection the views categorically expressed in my previous work (‘Entozoa,’ p. 387) cannot be maintained. What, however, is there stated in respect of _treatment_ still holds good in the main, even as regards prophylaxis.

BIBLIOGRAPHY (No. 30).--_Adam_, ‘Trans. Med. and Surg. Soc.,’ Calcutta, 1824.--_Aitken, W._, ‘The Science and Practice of Medicine,’ 6th edit., vol. i, 1872.--(Anonymous), “Review of the writings and opinions of Duncan, Johnson, Bird, Mylne, Kennedy, Chisholm, H. Scott, A. J. Robertson, Smyttan, Macgregor, Thomas, Mosely, Morehead, Twining, and others, on the Dracunculus or Guinea-worm,” in ‘Corbyn’s India Journ. of Med. and Phys. Sci.,’ vol. ii, p. 118, 1836.--(Anon.), “The Guinea-worm very Prevalent at Bokhara,” ‘Boston Med. and Surg. Journ.,’ 1843, p. 387.--_Balfour, J._, ‘Ind. Ann. Med. Sci.,’ 1859, p. 175.--_Ballingall, G._ (l. c., supra), 1854.--_Bastian, H. C._, “On the Structure and Nature of the Dracunculus or Guinea-worm,” ‘Linn. Soc. Trans.,’ vol. xxiv, p. 101, 1863.--_Berncastle, J._, in the ‘Lancet,’ 1851.--_Bird, J._, ‘Calcutta Med. and Phys. Trans.,’ 1825, p. 151.--_Bremser_ (l. c., Bibl. No. 2), s. 194.--_Brett_, ‘Surgical Diseases of India,’ 1840; see also ‘Med.-Chir. Rev.,’ 1841.--_Bruce, N._, ‘Edin. Med. and Surg. Journ.,’ 1806, vol. ii, p. 145.--_Busk, G._, ‘Micr. Soc. Trans.’ (original series), 1846.--_Carter, H. J._, “Note on Dracunculus in the Island of Bombay,” ‘Bombay Med. and Phys. Soc. Trans.’ (new series), No. 2, p. 45, 1853-54; see also postscript, p. 252.--_Idem_, “Further Observ. on Dracunculus,” ‘Bomb. Med. and Phys. Soc. Trans.’ (new series), No. 4, p. 215, 1857-58.--_Idem_, “On Dracunculus and Microscopic Filaridæ,” ‘Ann. of Nat. Hist.,’ vol. iv (third series), 1859.--_Idem_, “Notes on Dracunculus,” &c., ‘Ann. of Nat. Hist.,’ vol. ix (third series), 1862.--_Chapotin_, ‘Bull. des Sci. Med.,’ 1810.--_Charvet_, ‘Ann. des Sci. Nat.,’ 1834.--_Chiaje_ (l. c., Bibl. No. 2), p. 99.--_Chisholm, C._, “On the _Malis Dracunculus_ or Guinea-worm (in Grenada),” ‘Edin. Med. and Surg. Journ.,’ vol. xi, 1815; see also the ‘Veterinarian,’ vol. ix, p. 508, 1836.--_Clark_, ‘Med.-Chir. Rev.,’ 1840.--_Clarkson, N. F._, “Alleged Case in the Horse,” the ‘Veterinary Record,’ 1845, p. 73.--_Clot-Bey_, ‘Aperçu sur le ver dragonneau observé en Egypte,’ 1830.--_Cobbold_, ‘Entozoa,’ p. 373.--_Cuvier_, ‘Règne animal,’ Orr’s Eng. edit., 1849, p. 644.--_Davaine_, ‘Traité,’ l. c., edit. ii, p. 783 (full lit. refs.), 1878.--_Dickson_, ‘Path. Soc. Trans.,’ 1851.--_Drummond_, ‘Med. Commentaries,’ 1793, p. 294.--_Dubois_, ‘Edin. Med. and Surg. Journ.,’ vol. ii, 1806.--_Duncan_, ‘Calcutta Med. and Phys. Soc. Trans.,’ 1835.--_Ewart, J._, “Questions relating to Dracunculus,” in a review of his memoir on the “Vital Statistics of the Meywar Bheel Corps,” in the ‘Madras Quart. Journ. of Med. Sci.,’ vol. i, 1860, p. 462.--_Fedschenko_, ‘Protocol of the Promoters (Freunde) of the Natural and Physical Sciences at Moscow’ (in the Russian language), 1869 and 1874 (quoted by Leuckart).--_Forbes, D._, “Observ. on Dracunculus” (extr. from the ‘Half-yearly Reports of the diseases prevailing at Dharwar in the 1st Grenadier Regiment, in the year 1836’), ‘Bombay Med. and Phys. Soc. Trans.,’ vol. i, 1838, p. 215.--_Gibson, A._, “Note on the Prevalence of Dracunculus,” in his remarks on the “Diseases of the Deckan,” in ‘Bomb. Med. and Phys. Soc. Trans.,’ vol. ii, 1839, p. 209.--_Gramberg_, ‘Geneeskundige tijdschrift voor nederl. Indie,’ 1861, p. 632 (quoted by Leuckart).--_Greenhow, H. M._, ‘Indian Ann. of Med. Sci.,’ vol. vii, 1861, p. 31.--_Grierson, D._, “Observ. on the Dracunculus, as it prevailed in the 22nd Regiment, N.I., from April till September, 1841,” ‘Bomb. Med. and Phys. Soc. Trans.,’ No. 4, 1841, p. 90.--_Grundler_, in ‘Commerc. Litt. Nov.,’ 1740, p. 239.--_Henderson, J._, “Note respecting Four Cases of Dracunculus in the 48th Regiment,” ‘Madras Quart. Journ.,’ vol. iii, 1841, p. 353.--_Horton, J. A. B._, ‘Army Med. Reports,’ 1868, p. 335.--_Kennedy, R. H._, ‘Calcutta Med. and Phys. Soc. Trans.,’ 1825, p. 165.--_Küchenmeister_ (l. c., Eng. edit.), p. 389.--_Leuckart_ (l. c., Bibl. No. 1), s. 644-725.-- _Lewis, T. R._, in ‘On a Hæmatozoon,’ &c. (l. c., Bibl. No. 23), p. 30 _et seq._--_Lima, Da S._, “Remarks on the _Filaria medinensis_, or Guinea-Worm; on the occurrence of this Parasite endemically in the Province of Bahia; on its entrance into the human body by drinking water,” in the ‘Veterinarian,’ Feb., March, _et seq._, 1879.--_Lister_, ‘Phil. Trans.,’ 1690, p. 417.--_M’Clelland, J._, ‘Calcutta Journ. of Nat. Hist.,’ vol. i, 1841, p. 366.--_M’Grigor, J._, “On the Guinea-worm” (in his “Account of the Diseases of the 88th Regiment in Bombay”), ‘Edin. Med. and Surg. Journ.,’ vol. i, 1805, p. 284.--_Morehead, C._, ‘Calcutta Med. and Phys. Soc. Trans.,’ vol. vi, 1833, p. 418; also noticed in ‘Edin. Med. and Surg. Journ.,’ vol. xliv, 1835.--_Idem_, part ii, ‘Calcutta Med. and Phys. Soc. Trans.,’ vol. viii, 1836-42.--_Murray, J._, “Guinea-worm a very Common Disease at Sattara” (in his Official Report on the Hospital, &c.), ‘Bombay Med. and Phys. Soc. Trans.,’ No. 9, art. vi, p. 198, 1847.--_Oke, W. S._, “Case of Guinea-worm,” ‘Prov. Med. and Surg. Journ.,’ vol. vi, 1843.--_Oldfield_, “Case of Dracunculus” (from Laird and Oldfield’s “Narrative of an Expedition into the Interior of Africa”), ‘Dublin Journ.,’ vol. xii, 1838.--_Paton_, “Cases of Guinea-worm,” ‘Edin. Med. and Surg. Journ.,’ vol. ii, 1806.--_Raddock_, “A Case of Guinea-worm,” ‘Indian Med. Gaz.,’ Oct., 1877, p. 265.--_Scott, W._, “Remarks on the Dracunculus,” in a letter to the Medical Board, Madras, ‘Edin. Med. and Surg. Journ.,’ vol. xvii, 1821.--_Leverance, C. E._, “History of a Case of Guinea-worm,” from ‘Amer. Med. Times,’ in the ‘Glasgow Med. Journ.,’ vol. ix, 1861-62, p. 377.--_Smyttan, G._, “On Dracunculus,” ‘Calcutta Med. and Phys. Soc. Trans.,’ vol. i, 1825, p. 179.--_Stewart, L. W._, ‘Indian Ann. of Med. Sci.,’ vol. vi, 1858, p. 88.--_Twining, W._, “Cases of Dracunculus,” ‘Calcutta Med. and Phys. Soc. Trans.,’ vol. vii, 1835.

_Oxyuris vermicularis_, Bremser.--Of all the parasites infesting the human body this is the one concerning which the medical practitioner is most frequently consulted, partly on account of its remarkable frequency in children, and more particularly on account of the difficulty often experienced in getting permanently rid of it. The _Oxyuris vermicularis_ is by no means confined to young persons, seeing that adults are infested even to old age. It is familiarly known as the threadworm or seatworm. The male measures about 1/6″, and the female from 1/3″ to 1/2″ in length. The female possesses a long capillary tail, which terminates in a three-pointed end. The extremity is said to act as a kind of holdfast. The tail of the male is obtusely pointed. In both sexes the body presents a more or less fusiform shape, the anterior end being narrowed to form a somewhat abruptly-truncated head, which is often rendered very conspicuous by a bulging of the transparent integument surrounding the mouth. This presents in profile the aspect of winged appendages (fig. 45). The oral opening is tripapillated, leading into a triangular œsophagus. The integument is transversely striated, and of a silvery-white appearance. The spicule is simple, single, and very minute. The eggs are oblong and unsymmetrical. They measure about 1/900″ from pole to pole, and 1/1400″ transversely.

Many years back (1863) I pointed out that the most advanced eggs whilst still within the body of the pregnant female contained tadpole-shaped embryos, and about the same time the fact was noticed by Claparède. In his beautiful and scholarly memoir, ‘De la formation et de la fécondation des œufs chez les vers Nématodes,’ he wrote concerning the ova as follows:--“The egg, which exhibits the form of a very narrow disk in the ovary, acquires the shape of an elongated ellipsoid in the oviduct, and at the surface differentiates itself into a very thick vitelline membrane. Then it forms a strong and resisting chorion, which imparts to the egg an outline similar to that of a bridge’s span. It has an oval figure flattened at one of its sides. This chorion is very fragile; it frequently gives way under slight pressure from the thin plate of glass which covers the object. It extends itself considerably under the action of acetic acid, acquiring a size three or four times greater than that of the egg. The constitution of this chorion is perfectly identical in the eggs both before and after impregnation. It is, nevertheless, easy at first sight to know whether or not we have to deal with a fecundated egg. In the impregnated females the uteri are filled with thousands of ova, each one of which encloses an embryo already well formed. The ventral surface of the embryo and the tail are, without exception, applied to the flattened side of the egg. The embryo is very broad in the body, and occupies all the interior space. An embryo such as Küchenmeister has represented under the form of a small filiform worm folded on itself, and only occupying a very small part of the cavity of the egg, is never to be seen. In the non-fecundated females, on the other hand, the uteri are filled with eggs, which, instead of the embryo, enclose a non-segmented yolk furnished with a large germinal vesicle. This vesicle is not visible so long as the eggs have the form of thin disks; it only shows itself when the eggs begin to acquire an elliptical form in the oviduct. It is, however, probable that this vesicle is the same which was originally visible in the ovary.” The chorion itself is homogeneous, but in an allied species (_Oxyuris spirotheca_) Gyoery and Claparède found that this egg-covering consists of spirally-coiled bands resembling the tracheal spiral fibre of an insect. Under suitable conditions the tadpole-shaped embryos rapidly assume a vermiform character. The investigations of Leuckart have shown that “one only needs to expose the eggs to the action of the sun’s rays in a moistened paper envelope when, at the expiration of five or six hours, the tadpole-shaped embryos will have already become slender elongated worms.” According to Heller, the simplest way to rear the vermiform stage of Oxyuris is to put a number of the eggs in a glass tube filled up with saliva. The tube should then be placed in the arm-pit, in which situation it can be carried about with little inconvenience. In a few hours the transformations will commence and go on continuously until the vermiform condition is attained. If, as remarked in my ‘Lectures,’ it be asked whether the embryos which have escaped into the bowel are capable of arriving at the vermiform stage, the answer is in the affirmative; for, as Leuckart says, “the elongated embryos are to be found not only in the fæces but also in the mucus of the rectum above and around the anus.” Vix has also asserted that free vermiform embryos are occasionally to be detected in the intestine of the human bearer along with the eggs; this hatching within the lower bowel, however, must, in my opinion, be regarded as exceptional. Heller is of the same opinion. According to Leuckart, the escape of the embryos from the eggs “ordinarily takes place under the action of the gastric juice, also primarily in that condition when they have by some means or other gained access to a new bearer.” Prof. Leuckart and three of his pupils courageously infected themselves by swallowing the eggs, and had the satisfaction of observing young Oxyurides in their stools fifteen days afterwards.

From the united labors of Professors Zenker and Heller it is now rendered certain that all the further changes necessary to bring the larvæ to sexual maturity are accomplished within the small intestines of the human bearer; and it is not necessary that a change of hosts should occur at any time during the life of the parasite. Infection ordinarily takes place by the accidental and direct conveyance of the eggs that are lodged in the neighbourhood of the victim’s anus to the mouth. Since the victim may accomplish this during sleep, it is not in all cases fair to charge infected persons with uncleanliness. On the other hand, it too often happens that due care in this respect has not been exercised, and from such persons you may remove the eggs of Oxyurides from the margins of the finger nails. One aristocratic person, who was infested by myriads of these entozoa, confessed to me that in his extreme distress, and consequent rage, he had freely bitten the live worms in halves between his teeth. He had thus exposed himself to a terrible revenge, since multitudes of the ova entering his mouth subsequently found their way into the stomach and intestines. By whatever mode the eggs are conveyed to the mouth their subsequent passage to the stomach ensures their being hatched. In the duodenum and other divisions of the small intestines, as Zenker and Heller have shown, the embryos undergo transformation, casting their skins, and growing with great rapidity. Probably not more than three weeks or a month is necessary to complete their growth. Heller obtained mature worms from an infant only five weeks old. Finally the worms are transferred to the cæcum, which constitutes, so to speak, their headquarters. It is an error to suppose that the lower bowel or rectum forms their especial habitat, nevertheless the most approved manuals, vade mecums, and general treatises have for a long time supported this erroneous view. The error had been pointed out by Stricker in 1861.

The symptoms produced by Oxyurides are occasionally very serious. In the mildest cases they have a tendency to undermine the health. As remarked in my ‘Entozoa,’ the unpleasant sensations chiefly develop themselves in the evening and at night, consisting for the most part of feelings of heat and irritation within and around the margin of the anus. The symptoms may become extremely distressing and almost intolerable, especially when the itching extends to the genito-urinary passages, in consequence of the escape and migration of the parasites about these parts. By-and-by various sympathetic phenomena, such as restlessness, general nervousness, itchings at the nose, involuntary twitchings, grinding of the teeth during sleep, chorea, convulsions, and even epileptiform seizures, may supervene. At the age of puberty special local disorders arise, the nature of which will be readily understood when merely spoken of as the morbid phenomena of sexual irritation. In the female the occurrence of pruritus and leucorrhœa is not uncommon, accompanied or not, as the case may be, with hysteria in various forms. There is usually general asthenia, with more or less emaciation. The anæmia is sometimes remarkable, but in place of anorexia, which is, however, an occasional symptom, one frequently finds a most voracious appetite, especially in young people. Sometimes there are obscure symptoms simulating those of local organic disease.

About the treatment of the disorder I have nothing to say here, further than to urge the benefits of the preventive measure of cleanliness. Like Zenker and Heller, I have obtained the eggs of oxyurides from beneath the finger-nails of young people. In one lad all the nails had been carefully bitten down to their roots, but from beneath a minute projecting portion that was left on the right fourth-finger I procured two eggs. Their demonstration under the microscope convinced both parent and child of the necessity of frequently employing local and general ablutions. Personal cleanliness is essential. In this connection an able biologist has ventured to hazard a statement to the effect that “probably any infected person who adopted the requisite precautions against reinfection from himself or others would get well in a few weeks without treatment by drugs.” Dr Ransom bases his belief on the known facts of the life-history of this entozoon, as recorded more especially by Leuckart. I regret that I cannot fully share Dr. Ransom’s views, and still less should I think it right by my silence to seem to endorse his statement to the effect “that every person who is shown to be infested with those very common entozoa, _Oxyuris vermicularis_ and _Trichocephalus dispar_, is thereby demonstrated to have swallowed minute portions of his own or another person’s fæces.” This is putting the case too strongly. No doubt the eggs of oxyurides swallowed by ourselves must have previously passed through some person’s rectum; as such, either separately or mayhap collectively, in the body of the maternal parasite. That does not, however, justify the statement, that we “have swallowed” part of our own or of some other person’s excrement. The eggs ought not to be regarded as constituent portions of the fæcal matter. Perhaps Dr Ransom will say that the surfaces of these eggs, being in contact with fæcal matter, must carry infinitesimal particles on their surfaces, and it is to such that he refers. As, however, a large proportion of the ova escape with their parents, whilst they are still lodged within the maternal worm, it cannot be held that these intra-uterine ova carry fæcal matter on their shells. Commonly the eggs are swallowed in the separate, free, and dry state. In water they perish quickly. The act of eating with unwashed hands is a fertile source of infection, more especially if the meal be taken either in bed or in the bedroom.

BIBLIOGRAPHY (No. 31).--_Alexander, J._, “On Vermination,” ‘Lancet,’ 1833.--_Anderson, W._, “On Santonine, with especial reference to its use in Roundworm and Threadworm,” ‘Brit. Med. Journ.,’ April, 1864, p. 443; also in Braithwaite’s ‘Retrospect of Medicine,’ vol. xlix (synopsis, p. 20), 1864.--_Barry, J. M._, “On the Origin of Intestinal Worms, particularly the _Ascaris vermicularis_,” ‘Trans. Assoc. of Fell. and Licent. of King’s and Queen’s Coll. of Phys. in Ireland,’ vol. ii, 1878, p. 383.--_Bremser_, l. c., s. 79.--_Buckingham_, “Ascarides causing Erotomania,” from ‘Bost. Journ., U.S.,’ in ‘Med. Gaz.,’ 1857.--_Claparède, E._, “On the Formation of the Egg and Fertilisation in the Nematoidea,” from the ‘Zeitsch. f. w. Zool.,’ translated by Dallas in ‘Ann. Nat. Hist.,’ vol. i (third series), 1858.--_Idem_ (memoir quoted in the text above), Genève, 1859.--_Cobbold, T. S._, ‘Worms,’ Lect. xii-xv, 1872.--_Idem_, ‘Entozoa,’ p. 362.--_Idem_, ‘Brit. Med. Journ.,’ Aug., 1873.--_Idem_, ‘Tapeworms and Threadworms,’ 2nd edit., 1872.--_Idem_, ‘Lancet,’ 1866.--_Idem_, “On the Development and Migrations of the Entozoa,” ‘Brit. Assoc. Rep.,’ 1864, p. 116.--_Date, W._, ‘Lancet’ for Feb., 1872, p. 185.--_Davaine_, ‘Traité,’ l. c., 2nd edit., p. 211, and ‘Synops.,’ p. 95.--_Dickinson_, “Case of Epilepsy in Children relieved by the expulsion of Worms,” ‘Med. Times and Gaz.,’ Jan., 1863.--_Dickson, R._, art. “Anthelmintics,” rep. from the ‘Penny Cyclopædia,’ in Knight’s ‘Eng. Cyclop. Arts and Sci. Div.,’ vol. i (column 365), London, 1859.--_Dreyfus_, “Irritation of the Bladder from Ascarides,” from ‘Journ. de Med.,’ in ‘Lond. Med. Gaz.,’ 1847.--_Elliotson, J._, “A Lecture on Worms,” ‘Lond. Med. Gaz.,’ 1833.--_Idem_, “On Worms in the Intestinal Canal,” ‘Lancet,’ 1831.--_Idem_, “On a Case of Threadworms,” ‘Lancet,’ 1831.--_Idem_, “On Intestinal Worms,” ‘Lancet,’ 1830.--_Heller, A._, “Darmschmarotzer,” in von Ziemssen’s ‘Handbuch,’ Bd. vii, s. 632 (see also Anglo-American edit.), 1876.--_Küchenmeister_, l. c., Eng. edit., p. 356.--_Ransom_, in Reynolds’ ‘Dictionary of Medicine.’--_Smith, A._ (and others), ‘Lancet,’ April 29th, 1865, p. 468.--_Stricker, W._, in ‘Virchow’s Archiv,’ xxi, 1861, s. 360.--_Tatham_, ‘Lancet,’ April, 1867, p. 457; see also p. 519.--_Vix, E._, ‘Ueber Entozoen,’ &c., Berlin, 1860; see also “On the occurrence of Entozoa in the Insane, particularly with respect to the _Oxyuris vermicularis_;” brief notice (‘Allg. Zeitsch. f. Psychiatrie’) in Winslow’s ‘Journ. of Psycholog. Med.,’ vol. i, 2nd series, 1861, p. 158.--_Zenker_, ‘Verhandl. d. phys. med. Soc.,’ H. ii, Erlangen, 1870, s. 20; and in ‘Tageblatt der deutschen Naturforscherversammlung zu Dresden,’ 1868, s. 140 (also quoted freely by Leuckart, Davaine, and Heller).

_Leptodera_ (_Anguillula_) _stercoralis_, Bavay.--In the summer of 1876 Dr Normand, of the French Marine, discovered this little entozoon in the fæcal discharges of soldiers who had been sent home invalided from Cochin-China. The patients in question were the victims of the so-called Cochin-China diarrhœa or dysentery. This disorder is endemic in character, and it had hitherto been regarded as consequent upon a variety of causes other than parasitic. Dr Normand’s discovery, as such, therefore takes equal rank with the analogous revelations made by Bilharz, Harley, Leuckart, Zenker, Weber, Lewis, and Bancroft, in respect of the particular helminthiases in man with which their names are severally associated (Bilharzia disease, Endemic hæmaturia, Cestode tuberculosis, Olulaniasis, Inter-tropical anæmia, Trichinosis, Lymphoid affections, Helminthoma, and so forth), and also, if I may be permitted to say so, with my own determinations in respect of a variety of endemics affecting animals (cestode and nematode epizoöty in the horse, the so-called grouse-disease, the pigeon-endemic due to lumbricoids, &c.).

The _Leptodera stercoralis_ is a minute, smooth-bodied, simple, rhabditiform nematode, measuring when full grown 1/25″ in length, with an average breadth of 1/625 of an inch. The embryos at the time of their extrusion measure only 1/250″ in length, but by the time at which a rudimentary vesicle representing the uterus begins to form, the females have already attained a length of about 1/83″. The males and females are of nearly equal size. The transition from the embryonal state to the higher larval conditions is accompanied by a change of skin, after which the digestive and reproductive organs are gradually but rapidly formed and completed. These changes have been minutely traced and recorded by Professor Bavay, who also compares the entozoon with the genera Rhabditis and Leptodera, in either of which genera the worm might be placed. I have accordingly adopted the nomenclature suggested by Bavay.

As happens in all the kindred helminthiases that are known to be dependent upon the presence of small worms, large numbers of Anguillules are necessary to produce injurious effects upon the bearer. Thus, the evacuations of the Cochin-China patients were found to contain such multitudes of the worms that their numbers could only be adequately estimated at so many hundreds of thousands passed in twenty-four hours. Of course they varied in quantity, not only in different patients, but in the same bearer, from day to day. They are to be found in every stage of growth and development, from that of the intra-ovular embryo and free embryonic state up to sexual maturity. They occupy all parts of the intestinal canal, from the stomach downwards, being also found in the pancreatic and biliary ducts, and likewise within the gall-bladder. According to Bavay, five days suffice under favorable circumstances for the complete maturation of the worm. This readily accounts for their occasional extreme abundance.

I am indebted to the courtesy of Dr le Roy de Méricourt for the original memoirs from which these brief abstracts are taken.

_Leptodera intestinalis_, Bavay.--This is a larger species, now and then found associated with the above, and, according to Bavay, “in infinitely less abundance.” This species was also discovered by Dr Normand, and has been carefully described by Bavay. Possibly the worm may afford us another curious instance of dimorphism. Be that as it may, it must be provisionally regarded as a distinct form. As its occurrence is by no means invariable, its rôle in relation to the Cochin-China diarrhœa must, as Davaine has likewise remarked, be regarded as of secondary importance. It is readily distinguished from _A. stercoralis_ both in the adult and larval conditions. The full grown worm, although comparatively narrow, is more than twice as long as its congener; moreover, the larvæ, in place of possessing finely-pointed tails, have blunt or truncated caudal extremities. Converting M. Bavay’s millimetric measurements into fractions of the English inch, the average length of the mature worms will be about 1/11″, whilst their breadth does not exceed 1/757″ in diameter.

BIBLIOGRAPHY (No. 32).--_Bavay_, “Sur _l’Anguillule stercorale_,” ‘Comptes Rendus,’ Oct., 1876, p. 694, also in ‘Ann. Nat. Hist.,’ vol. xviii, 4th series, p. 507, 1876, also noticed in the ‘Veterinarian,’ Jan., 1877, p. 19.--_Idem_, “Note sur _l’Anguille intestinale_,” ‘Archiv. de Méd. Nav.,’ July, 1877, p. 64, and in ‘Ann. Nat. Hist.,’ 1877, vol. xix, 4th series, p. 350.--_Cobbold, T. S._, “Parasites of Man,” in the ‘Midland Naturalist’ for January 1st, 1879.--_Davaine_, ‘Traité,’ l. c., 2nd edit., Supp., pp. 966-976, 1877.--_Laveran_, in ‘Gaz. Hebd. de Med.,’ Jan., 1877, p. 42.--_Layet_ and _Le Roy de Méricourt_, in ‘Dict. Encycl. des Sci. Med.,’ 1875.--_Libermann_, in ‘Gaz. des Hôp.,’ March, 1877, p. 237, and in ‘La France Méd.,’ 1877, p. 165 (quoted by Davaine).--_Méricourt_ (see Layet).--_Normand, A._, in ‘Comptes Rendus’ for July, 1876, p. 316, and Aug., 1876, p. 386.--_Idem_, in ‘Arch. de Méd. Navale,’ 1877, p. 35, and separately as ‘Mémoire sur la diarrhée dite de Cochinchine,’ Paris, 1877.--_Idem_, “Du rôle étiologique de l’Anguillule dans la diarrhée de Cochinchine,” in ‘Archives de Médecine Navale’ for September, 1878, pp. 214-224.

_Ascaris mystax_, Rudolphi.--This well-known helminth possesses aliform appendages, one on either side of the head. It is of a medium size, the male measuring 2-1/2″ and the female usually 3-1/2″ to 4″ in length. Both as regards the size of the alæ and the length of the body it varies in different hosts. Thus the variety infesting the dog has long been regarded as a distinct species (_A. marginata_), partly from the circumstance that the alæ are less conspicuous, and partly because the individuals are often longer and thicker. I possess one specimen from the dog measuring more than six inches in length. From like causes the _Ascaris leptoptera_ and other varieties infesting the carnivora have been regarded as distinct species, but the worm also varies in one and the same host.

As remarked in my elementary treatise, the late Dr Bellingham, of St Vincent’s Hospital, Dublin, published in the 13th vol. of the ‘Annals of Natural History,’ an extended catalogue of Irish entozoa, and in this list he recorded the existence of a new round worm in man. He says of it:--“From the distinctness of the lateral membranes of the head I have given it the name of _Ascaris alata_.” The catalogue was constantly referred to by Dujardin, Diesing, and other systematists; but some of the continental helminthologists do not appear to have had access to Dr Bellingham’s more extended account of this parasite as given in the first volume of the ‘Dublin Medical Press,’ No. 7, Feb. 20th, 1839. I am led to this inference from the doubt which some have cast upon the very existence of the worm, although others, with more candour, supposed that Bellingham had only mistaken the species. Thus, Küchenmeister (‘Parasiten,’ s. 464, and in Lancaster’s edit., vol. ii, p. 100) says:--“The _Ascaris alata_, found in the small intestines of a man, is probably only a young individual of one of the long-known nematoda, _if, indeed, it be a worm at all_!” (The italics are mine.) This statement was reproduced by Hulme in his English edition of Moquin-Tandon’s ‘Elements of Medical Zoology,’ p. 341; and the French author himself evidently shared the doubt expressed by other people. Dujardin (‘Helminthes,’ p. 156) admitted the species, as also did Diesing (‘Systema Helminthum,’ p. 175), but the latter unluckily added the following very significant suggestion:--“An _Ascaris lumbricoides_ capitis epidermide emphysematice inflata?”

Dr Leidy, of Philadelphia, admitted _A. alata_ among his _Entozoa hominis_ without comment (‘Smithsonian Contrib.’ for April, 1853), but Weinland, of Frankfort, in his list, prefixed a note of interrogation, observing also that it had been “once” found in Ireland (‘Essay on Tapeworms,’ p. 88). It is quite clear, therefore, that these authors did not believe that the _Ascaris mystax_ was a human parasite. Those who doubtfully accepted Bellingham’s _A. alata_ did so under the impression that whatever it was, it could not be regarded as the common Ascaris of the cat. In the new edition of Davaine’s ‘Traité,’ _A. alata_ is, to my surprise, still retained as a separate species, and there is no mention of the occurrence of _A. mystax_ in man. From what has recently been written by several continental helminthologists (Leuckart, Heller, and others), I rejoice to think that it is not necessary for me again to advance the really superabounding proofs that Bellingham’s _A. alata_ was nothing more than _A. mystax_. It has at length been admitted by almost all who are competent to form an opinion, that the memoir originally communicated to the ‘Lancet,’ in 1863, and subsequently introduced into the text of my introductory work, finally settled the question of identity. It was through the donation of Dr Edwin Lankester and Mr Scattergood that I was enabled at the time to announce the _third instance_ of the occurrence of this parasite in man, and since that date several other instances have been brought under public notice. Not less than seven cases have now been noticed in which this little lumbricoid of the cat and dog has been found in man. For one good human specimen I am indebted to Dr Morton. In the above list I include Heller’s specimen, and the one from Greenland sent by Steenstrup to Leuckart. According to Hering’s observations this worm grows with remarkable rapidity. Worms obtained from a puppy only six days old measured from 1/12″ to 1/6″ in length. In a twelve-day-old puppy they reached nearly an inch in length, and in a month the growth was up to four inches. Females only 1-1/2″ in length already contained eggs, and males only 3/4″ long had acquired their spicules. Three weeks therefore, would be amply sufficient for the completion of sexual maturity within the feline or canine host. We do not know, however, whether or not a temporary host is necessary for the larvæ prior to their introduction into the cat or dog. Hering thinks that a direct infection by the ova is sufficient; but he gives no proof of the truth of this hypothesis. “Leuckart (as quoted by Heller, l. c., s. 615) found numerous embryonal round worms in the stomach of a cat, 1/62″ in length, and in addition all the intermediate stages of growth up to the larger examples found in the small intestine. They remain in the stomach until they have attained a length of from 1/18″ to 1/12″ and then pass into the small intestine. When they have attained a length of nearly 1/8″ they cast their skins and change the tooth-like boring apparatus for the three characteristic semicircular lips. These observations on _Ascaris mystax_ (adds Heller) render it probable that _A. lumbricoides_ is also introduced into the human alimentary canal while still in the embryonal state or somewhat further advanced (und wohl auch grösse).” The subject will be found more fully discussed in my account of the large species further on. The cat’s worm possesses an historical interest, not only in connection with Bellingham’s original discovery, but also in respect of Nelson’s subsequent determinations as to the precise mode of impregnation in nematodes. The subject is too extended and too special to be dealt with here at any great length.

For several years after Nelson left the shores of England to spend a too short life in New Zealand, the points discussed in his ‘Edinburgh Thesis’ (and subsequently published in the ‘Philosophical Transactions’) formed the subject-matter of numerous memoirs contributed to the leading German scientific journals. Stated with brevity, it may be said that, according to Nelson, the essential act of impregnation occurs when the thimble-shaped spermatozoa of the male penetrate the unimpregnated or ovarian ovum. This, he maintained, could and did take place at any part of the surface of the unfertilised ovum, since the granular mass of which it was composed, though well defined, did not, at this period, possess a limiting--or true yolk--membrane. Professor Allen Thomson, in a series of papers (some contributed in the German language), supported Nelson’s views generally.

Amongst Nelson’s chief opponents was Meissner, who demonstrated that the unimpregnated ova really possessed a delicate limiting membrane, and that consequently the action of the spermatozoa was restricted to that portion of the ovarian ovum which became exposed by rupture or separation from the rachis. This opening he termed the micropyle. The union of the sexual elements is quickly followed by a condensation of the yolk-granules, and by the disappearance of the hitherto centrally placed germinal vesicle. The ovum next assumes a distinctly oval shape, the true yolk-membrane and the external chorional envelope now becoming more and more differentiated, until the latter acquires a regularly tuberculated surface. Co-ordinating with these changes the granular yolk is seen transforming itself into a single large embryonal cell; after a time this cell divides and subdivides by the ordinary process of yolk-segmentation, until it is finally resolved into the condition of a short, stout, vermiform embryo. The egg having assumed its definitive oval shape, the intrachorional embryo remains coiled within the shell, and does not make its escape until the egg has passed from the body of the parent worm.

Into the question of the mode of formation of the ovarian ova, and also into that of the development of the spermatozoa, I do not enter. However unwillingly, I must, in this matter, be contented to refer to Professor Allen Thomson’s classical article ovum (quoted below), to Leuckart’s elaborate analysis (l. c., Bd. ii, s. 76-92), and also, especially, to the exhaustive memoir of Claparède, whose brilliant labors, like those of Henry Nelson, were too early terminated by death. Shortly after graduation Nelson suffered a virtually enforced banishment from his native land.

BIBLIOGRAPHY (No. 33).--_Bellingham, O. B._, “On the Genus to which the Worms known as Ascarides belong,” ‘Dublin Journ.,’ vol. xiv, 1839.--_Idem_, “Catalogue of Irish Entozoa,” ‘Ann. of Nat. Hist.,’ vols. xiii and xiv, 1843-44; and in the first part of Charlesworth’s ‘Mag. of Nat. Hist.,’ vol. iv, 1840. See also the address by Dr E. D. Mapother on the “Lives and Writings of O’Ferrall and Bellingham,” in the ‘Dubl. Journ. of Med. Sci.,’ Nov., 1877, p. 471 _et seq._--_Bischoff_, ‘Widerlegung (u. s. w.),’ Giessen, 1853; quoted by Claparède, l. c. _infra_, p. 9.--_Idem_, ‘Bestätigung (u. s. w.),’ Giessen, 1864.--_Idem_, “Ueber Ei-und Samenbildung und Befruchtung bei _Ascaris mystax_,” Sieb. and Köll. ‘Zeitsch.,’ 1855, s. 377; also in S. and K. ‘Zeitsch.,’ 1856.--_Bremser_, ‘Icones helminth.,’ p. 23, tab. iv.--_Claparède, E._, “Ueber Eibildung und Befruchtung bei den Nematoden,” S. and K. ‘Zeitsch.,’ 1857, s. 106.--_Idem_, ‘De la formation et de la fécondation des œufs chez les vers Nématodes,’ Genève, 1859. See also ‘Ann. of Nat. Hist.,’ vol. i, 3rd series, 1858.--_Cobbold_, in ‘Proceed. of the Zoological Soc. of London,’ Nov., 1862.--_Idem_, ‘Brit. Assoc. Rep.,’ 1862.--_Idem_, “On the occurrence of _Ascaris mystax_ in the Human Body,” with figures, ‘Lancet,’ Jan., 1863; and in the ‘Dublin Med. Press,’ Feb., 1863.--_Idem_, ‘Entozoa,’ chap. xi, p. 316, 1864.--_Idem_, ‘Worms,’ pp. 72 and 112, 1872.--_Idem_, in “Obituary Notice of Dr Henry Nelson,” ‘Med. Times and Gaz.,’ 1865 (?).--_Davaine_, ‘Traité,’ l. c., 1877.--_Diesing, C. M._, ‘Syst. Helm.,’ vol. ii, p. 180, 1850.--_Dujardin_ (l. c., Bibl. No. 2), p. 162.--_Frœlich_, in ‘Naturf.,’ xxiv, s. 141 (_Asc. felis_).--_Funke, O._, ‘Lehrbuch (u. s. w.),’ 1857, s. 1299.--_Gmelin_, ‘Syst. Nat.,’ p. 3031.--_Golze_, ‘Naturg.,’ l. c., s. 79.--_Gurlt_, ‘Path. Anat.,’ s. 366.--_Heller, A._, “Darmschmarotzer,” in Von Ziemssen’s ‘Handbuch,’ Bd. vii, s. 361.--_Idem_, ‘Sitzungsb. d. Erlanger phys.-med. Soc.,’ 1872, s. 73.--_Hering_, “Ueber das Vorkommen und die Entwicklung der _Ascaris mystax_ bei jungen Hunden,” quoted by Leuckart from ‘Würtemb. Naturw. Jahreshefte,’ 1873, s. 305-337.--_Kölliker_, in ‘Müller’s Archiv,’ 1843, s. 68 _et seq._--_Leidy_, ‘Proc. Acad. Phil.,’ viii, p. 50.--_Leuckart_, l. c., Bd. ii, s. 258.--_Meissner, G._, “Beobachtungen über das Eindringen der Samenelemente in den Dotter,” S. and K. ‘Zeitsch.,’ 1854, s. 208.--_Morton, T._, “Another Example of the Occurrence of _A. mystax_, from a Child of fourteen months old,” in a letter to the ‘Lancet,’ March 11th, 1865, p. 278.--_Nelson, H._, “On the Reproduction of _Ascaris mystax_,” ‘Proc. of the Royal Soc.,’ in ‘Philosoph. Trans.,’ and in ‘Med.-Chir. Rev.,’ 1051-52; also in ‘Froriep’s Tagsbericht.,’ 1852, s. 205-207.--_Rudolphi_, ‘Synops.,’ p. 42, 1819.--_Schneider_, “Ueber Bewegung an dem Samenkörperchen der Nematoden,” in ‘Monatsb. d. Berliner Akad.,’ 1856, s. 192.--_Idem_, ‘Monographie der Nematoden,’ Erste Abth., s. 38, und Dritte Abth., s. 263 (“Entwicklungsgeschichte”), 1866.--_Siebold_, ‘Vergleichende Anatomie,’ 1848, s. 153, and in Burnett’s edit., p. 125 _et seq._, 1854.--_Thomson, A._, art. “Ovum,” in ‘Todd’s Cyclop. of Anat. and Phys.,’ supp., 1859.--_Idem_, “Ueber die Samenkörperchen, die Eier und die Befruchtung der _Ascaris mystax_,” S. and K. ‘Zeitsch.,’ 1856, s. 425.--_Idem_, “Report of Glasgow Meeting” (‘Brit. Assoc. Rep.’), 1855, p. 158.

_Ascaris maritima_, Leuckart.--This is a well-marked species. Judging from the characters presented by the solitary, sexually-immature female which supplied Leuckart with his only means of diagnosis, this worm may be briefly described as a filariform nematode about 3/4″ in length and about 1/25″ in breadth. Although there are no cephalic aliform membranes, the cuticle immediately below the lips forms small and distinct projections, one on either side of the head (‘Die Mensch. Par.,’ Bd. ii, s. 877).

This entozoon was discovered by Dr Pfaff at Jacobshavn, near Godhavn, West Greenland, in April, 1865. Two years later he sent the specimen to Krabbe, who afterwards transmitted it to Leuckart. In the original communication addressed to the Copenhagen helminthologist, Dr Pfaff states that he procured the worm from amongst matters vomited by a child, and he incidentally observes that he had hitherto encountered only _Bothriocephalus cordatus_ and _Oxyuris vermicularis_ amongst Greenlanders. As to the source of infection, Prof. Leuckart not unnaturally refers to the similar conditions of existence shared by the human and carnivorous inhabitants of that country. It is well known that bears, polar-bears, seals, and walruses are largely infested by nematodes (_Asc. transfuga_, _A. osculata_, _Ophiostoma dispar_, &c.), but these various species are quite distinct from Dr Pfaff’s little “spulwurm.”