122 



ENTOZOA. 



Fig. 66. 



Fig. 67. 



Diplostomum volvens in the eye of a Perch. 



parasite, which sometimes exists in such pro- 

 digious numbers, that the cavity of the eyeball 

 is almost exclusively filled by them. They 

 not only infest the vitreous but also the aqueous 

 humours, and have been found in the choroid 

 gland. 



All the species of Diplostomum are very 

 small, seldom exceeding a sixth part of a line 

 in length. They resemble the genus Distoma, 

 and present some affinity to" the Cercaria, 

 which infest the fresh-water Snails ; but they 

 have characters peculiar to themselves which 

 entitle them to rank as a distinct genus ; of 

 these the principal external one is the addi- 

 tional sucker developed on the ventral aspect 

 of the body, as compared with Distoma, 

 whence Nordmann calls the genus Diplosto- 

 mum, though Diplo-cotylus would be the more 

 appropriate designation, since, as before ob- 

 served, the ventral depressions are simply 

 organs of adhesion, and have no communication 

 with the alimentary canal. Besides the suckers 

 the Diplostomum has an anterior mouth (a, jig. 

 81), as in the Distoma. The first or anterior 

 sucker (b,Jlg. 81 ) is twice the size of the mouth; 

 and the second (c,jig.Ql) is again double the 

 size of the former. As the figure shows the 

 vessels from the dorsal aspect, these suckers 

 can only be seen in outline. The animal has 

 great power over them and can contract the 

 parenchyma of the body surrounding them, 

 so as to make them project like rudimental 

 extremities from the ventral surface. 



It has been already observed that no species 

 of the Acanthocephalous order of Entozoa has 

 hitherto been found in the Human body, the 

 illustration of this form of the Sterelmintha 

 will therefore be confined to the section treat- 

 ing of the general anatomy of the Entozoa. 



The Class Calelmintha contains several 

 species of Entozoa which are obnoxious to 

 man; of these may be first mentioned the 

 Medina or Guinea-worm (Filaria Medinensis, 

 Gmel.) This species is developed in the sub- 

 cutaneous cellular texture, generally in the 

 lower extremities, especially the feet, sometimes 

 in the scrotum, and also, but very rarely, be- 



neath the tunica conjunctiva 

 of the eye. It appears to be 

 endemic in the tropical regions 

 of Asia and Africa. 



The length of this worm 

 varies from six inches, to two, 

 eight, or twelve feet; its thick- 

 ness from half to two-thirds 

 of a line; it is of a whitish 

 colour in general, but some- 

 times of a dark brown hue. 

 The body is round and sub- 

 equal, a little attenuated to- 

 wards the anterior extremity. 

 In a recent specimen of small 

 size, we have observed that the 

 orbicular mouth was surround- 

 ed by three slightly raised 

 swellings, which were conti- 

 nued a little way along the 

 body and gradually lost ; the 

 body is traversed by two lon- 

 gitudinal lines corresponding 

 to the intervals of the two well- 

 marked fasciculi of longitu- 

 dinal muscular fibres. The 

 caudal extremity of the male 

 is obtuse, and emits a single 

 spiculum; in the female it is 

 acute and suddenly inflected. 



The Filaria Medinensis, as 

 has just been observed, is oc- 

 casionally located in the close 

 vicinity of the organ of vision ; 

 but another much smaller spe- 

 cies of the same Genus of 

 Nematoidea infests the cavity 

 of the eyeball itself. 



The Filaria oculi humani 

 was detected by Nordmann in 

 the Liquor Morgagni of the 

 capsule of a crystalline lens of 

 a man who had undergone the 

 operation of extraction for ca- 

 taract under the hands of the 

 Baron von Grafe. In this in- 

 stance the capsule of the lens 

 had been extracted entire, and 

 upon a careful examination 

 half an hour after extraction 

 there were observed in the fluid 

 above-mentioned two minute 

 and delicate Filaria coiled up 

 in the form of a ring. One of 

 



microscopically, presented a rupture in the mid- 

 dle of its body, probably occasioned by the ex- 

 tracting needle, from which rupture the intesti- 

 nal canal was protruding ; the other was entire 

 and measured three-fourths of a line in length ; 

 it presented a simple mouth without any appa- 

 rent papillae, (as are observed to characterize 

 the large Filaria which infests the eye of the 

 Horse,) and through the transparent integument 

 could be seen a straight intestinal canal, sur- 

 rounded by convolutions of the oviducts, and 

 terminating at an incurved anal extremity. 



The third species of Filaria enumerated 

 among the Entozoa Hominis is the Filaria 



