ENTOZOA. 47 



surrounds their mouth. In the Echinococcus Veterinorum, the 

 species which infests the common domestic animals, the oral spines, 

 when retracted, offer a close resemblance to the cylinder of teeth, 

 which characterises the Nassula {Jig. 11.) and manj^ other Poly- 

 gastria. The body of this Echinococcus likewise presents a number 

 of clear globules resembling hyaline, and very similar to the 

 so-called stomachs of the Polygastria. In an acephalocyst, from 

 the abdomen of a recently killed hog, I observed these little creatures 

 moving in the fluid, apparently by the action of superficial vibratile 

 cilia, thus adding a remarkable feature to their resemblance to the 

 Polygastria. The Echinococci, from a small musk-deer, lately dis- 

 sected at the College, closely resemble those of the hog, which I 

 have elsewhere described * ; but, being dead, the ciliated structure is 

 not indicated, and could not be detected. Each tooth or spine 

 presents an elongated triangular form, a small process extending from 

 the middle of its outer margin, probably for the attachment of the 

 protractor fibres. 



The Echinococci of the human subject {fig. 18.), which have been 

 accurately described by Professor Miiller in a case where 

 they were developed in the urinary bladder, and which 

 have been carefully figured by Mr. Quekett in a case ob- 

 served by Mr. Curling, where they were developed in the 



Echinococcus .,,.,,. ^ 



hominis. liver, wcre in both cases inhabitants of a cyst, rather the 

 parasites of an acephalocyst than of the human body. These Echi- 

 nococci difi"er from those of the hog in having suctorious cavities (6), 

 external to the circle of teeth («), and thus closely resembling the 

 head of a Taenia, appended to a small cyst. 



The hydatid developed in the substance of the brain of sheep and 



rabbils, called Ccenurus cerebralis, consists of a large cyst, with which 



many heads, like those of the Tsenioe, are in organic connection. 



19 These can be retracted within, or protruded without, the 



common cyst. 



The genus Cysticercus is characterised by having only 

 a single uncinated and suctorial head, connected by a 

 neck or body, sometimes annulated, and of greater or less 

 length, with the terminal cyst. Of this genus one species, 

 Cysticercus Cellulosce {Jig. 19.), is occasionally developed in 

 the human subject. It has been met with in the eye, the brain, the 

 substance of the heart, and the voluntary muscles of the body. The 

 peculiar inflammation which it excites leads to the formation of a 



* Art. " Entozoa," Cyclopa'dia of Anatomy and Pliysiology, p. 158. 



