66 LECTURE IV. 



The genus Cysticercus is characterised by having only a single 

 25 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 cellu- 

 losce {Jig. 25.), is occasionally developed in the human sub- 

 ject. It has been met with in the eye, the brain, the sub- 

 stance of the heart, and the voluntary muscles of the body. 



Cysticercus ^ •' "^ 



ceiiuiosae. The pcculiar inflammation which it excites leads to the form- 

 ation of a condensed bag of cellular tissue around it, which, in the 

 muscular tissue, lengthens in the direction of the fibres, and so im- 

 presses an oval form upon the Cysticercus : but this form does not 

 characterise the specimens developed in the softer tissue of the brain 

 or liver. The Cysticercus cellulosce is generally about half an inch 

 in length. 



The most common hydatid in the ox and other ruminants, is a 

 large species of the present genus, called Cysticercus tenuicollis, 

 which has been found weighing 25 drachms and containing 3 oz. 

 of fluid. In these much-expanded Cysticerci muscular fibres are 

 developed in different directions in the substance of the cyst, and 

 produce lively contractions. The clear calcareous corpuscles which 

 in Ccenurus and Echinococcus are scattered through the walls of the 

 cyst immediately under the skin, in the Cysticercus are exclusively 

 aggregated in the undistended part of the animal called the " neck." 

 In the progress of the accumulation of the fluid in the main body, 

 shreds of the tissue get occasionally detached from the inner surface 

 of the dropsical cyst, and are occasionally seen hanging from the 

 base of the neck and floating in the fluid.* In the oral circle of 

 spines, these are arranged in a double row alternately long and short, 

 and from twenty to thirty in number. The four suckers are im- 

 perforate. This well-armed head may serve to irritate the interior 

 of the adventitious cyst and excite the secretion on which the pa- 

 rasite subsists.! All the Cysticerci manifest their affinity with the 



Cestoidea by the organisation of their head, and this is more strikingly 

 illustrated by the length and segmentation of the body, with the 

 comparatively small size of the cysts, in the Cysticercus fasciolaris, 

 which is commonly found encysted in the liver of the rat and mouse. 

 The question of the larval relation of all the above- described cystic 

 entozoa to the Cestoidea will be entered upon after a description of 

 the latter, to which I shall next proceed : limiting myself chiefly, in 

 regard to the organisation of the Tapeworms, to the two species 

 which infest the human intestines ; namely, the Tcenia solium and 



* LXII. p. 205. f LXI. p. 183. 



