64 ANIMAL PARASITES. 



Of the intermediate stratum containing the vessels, it still 

 remains to be remarked in general, that it is finely granular, 

 tenacious, and of a cloudy, and, here and there, brownish ap- 

 pearance ; sometimes blended into a continuous layer, sometimes 

 into flakes, and that it bears cleft fibres, which are swelled up, 

 and contain fat-granules at the points of cleavage. The inner- 

 most stratum, the residue of the medullary layer, has its previously 

 clear vesicles filled with fat, even with fat-drops. It is probable 

 that in this way is brought about a peculiar morbid process, 

 which I have met with in a single instance amongst several 

 hundred Cysticerci tenuicolles which I have examined. The 

 caudal vesicles were completely set with small white points, per- 

 fectly visible to the eye, which, under the microscope, presented 

 nothing like calcareous corpuscles, but rather a fatty mass en- 

 closed in a tolerably firm tissue, whilst at the neck of the vesicle 

 a second small vesicle made its appearance, which contained fluid, 

 and was not separable from the tissue of the neck. In this dis- 

 covery I recognise the morbidly degenerated embryonic body of a 

 Cysticercus tenuicollis, and, at the same time, a fresh support for 

 my statements regarding the normal and healthy nature of the 

 ordinary caudal vesicle of the Cysticerci. 



From the moment when the formation of the cephalic process 

 commences, the caudal vesicle ceases its activity in the true 

 Cysticerci ; its functions are then only passive, serving as a reser- 

 voir of nutriment, as a protective organ for the head, which 

 requires repose for its further development, and as an organ 

 which may at the same time also preserve sufficient room for the 

 undisturbed development of the head. 



The case is certainly different in the cystic worms with 

 multiple proliferation. In these, as already remarked, besides 

 the last-mentioned function, the embryonal vesicle constantly 

 executes the proliferation at repeated intervals, and on the 

 most various parts, both in the Ccenuri and Echinococci. Here, 

 therefore, we can no longer speak of the remains of the 

 embryonal vesicle as a true caudal vesicle. On the hollow 

 cephalic process itself, various metamorphoses commence at dif- 

 ferent times in the different species, but at any rate not before 

 the fourth week after administration. In the process which is, 

 as it were, introverted in the caudal vesicle, and which, with its 

 flask-shaped cavity represents, as already observed, the first foun- 

 dation of the head of the tape-worm, and, indeed, in the lower 



