198 ENTOZOA FOUND IN MAN. 



The cysticerci developed in the brain sometimes 

 exist in great numbers, either accumulated in one part 

 only or, as is more generally the case, disseminated 

 throughout the whole encephalon. In the majority 

 of cases, the cysticerci are situated in the cerebral 

 substance, in the pia-mater, and in the choroid 

 plexuses ; they are also occasionally found in the 

 membranes of the brain. 



Like the hydatids, the cysticerci are invested by 

 a delicate covering of areolar tissue, which serves the 

 purpose of a cyst for them ; when they are situated 

 in the interior of the brain, the cyst is very fine, or 

 consists only of a few filamentous shreds. 



The cysticerci situated in the brain are often 

 found to have undergone marked changes of struc- 

 ture. The vesicle becomes more globular, and is 

 occasionally divided into lobules, or into two distinct 

 portions ; the head, the rostellum, and the suckers 

 of the entozoon are covered by a deposit of black, 

 pigmentary matter ; at a more advanced period 

 the hooks diminish in number, or even disappear 

 altogether ; the contracted or obliterated opening of 

 the vesicle does not permit of the protrusion of the 

 body, and the head, which is invaginated in the 

 latter, can only be extracted from it by carefid 

 pressure. 



These changes bear an evident relation to the 

 age of the cysticerci. The difierences which they 

 produce in the appearance of these entozoa have 

 been regarded as natural to their growth by some 

 helminthologists, whilst other writers have considered 

 them as sufficiently characteristic to admit of the 

 classification of the cysticerci into several species. 

 (Vide " Synopsis," page 19.) 



