Parasites: A Treatise on the Entozoa of Man and Animals / Including Some Account of the Ectozoa

by T. Spencer Cobbold

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 21/2″ and the female usually 31/2″ 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 11/2″ 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.

Fig. 49.—Germs and ova of Ascaris mystax. Nos. 1 to 3 magnified 330 diameters and Nos. 4 to 24 magnified 220 diameters. After Nelson.

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.