112 ENTOZOA. 



divisions — an outer limiting line forming the " receptaculum 

 capitis," and an inner one encircling the "central cephalic mass." 

 Traces of a skin- skeleton under the form of " calcareous particles " 

 also make their appearance in the substance of the receptaculum, 

 becoming extremely abundant in this situation at a still later 

 period. Formerly these calcareous corpuscles were regarded as 

 morbid formations, but the view above taken has now gained very 

 general acceptance. Contemporaneously with the formation of the 

 corpuscles, Leuckart also found vessels between the muscular and 

 epidermic layers ; these vessels are said to contain a clear, limpid 

 fluid, circulated by means of cilia. 



It should be noted that only a certain proportion of the little 

 vesicles (which at first appear so numerously scattered throughout 

 the substance of the rabbit's liver) pass through the develop- 

 mental changes above described. This would seem to be owing 

 either to their being originally too numerous to admit of their 

 growth within the infested organ, or, as Kuchenmeister obsei"ves, 

 " they do not find a favourable soil for their further development." 

 After the lapse of fourteen or fifteen days the aborting vesicles 

 commence a kind of retrograde metamorphosis, passing, he adds, 

 " to the state of caseous, granular, tubercular, or atheromatose 

 masses, in which we may generally seek in vain for any remains of 

 the embryo." These appearances are famihar to all helmin- 

 thologists. 



From Leuckart' s researches it would seem that towards the 

 close of the third or beginning of the fourth week, some of the 

 young cysticercs make their escape into the abdominal cavity of 

 the rabbit ; in this case, remaining enveloped ia their cysts of 

 connective tissue, and pushing the peritoneal covering of the hver 

 before them. In this condition we often find them loosely sus- 

 pended in the abdominal cavity. Others escape in a more 

 advanced state (at the fifth and sixth week) ; they are independent 

 of their cystic envelope, and may be found wandering over all parts 

 of the abdomen. By this time these "wandering larvas" have 



