16 ENTOZOA FOUND IN MAN. 



1. The Six-hooked Embryo ; 



2. The Hydatid ; 



3. The Echinococcus ; 



4. The Proglottis. 



According to the nomenclature of Van Beneden 

 the second phase would be called the Proscolex, and 

 the third (and penultimate) phase the Scolex ; the 

 more homely nomenclature of Steenstrup would 

 furnish the designation of Grand-nurse for the 

 hydatid, and of Nurse for the echinococcus. 



Certain experiments, which consisted in causing 

 dogs to swallow a large number of echinococci, have 

 been made by Von Siebold, and rejDeated by Van 

 Beneden, and their observations have led these dis- 

 tinguished writers to conclude that the echinococcus 

 becomes developed into a perfect taenia in the intes- 

 tinal canal of the dog. 



Hydatids are not developed in a cavity invested 

 with a mucous membrane, but in serous cavities, or 

 in the substance of various organs ; and, in the latter 

 case, they are always enclosed in an adventitious 

 cyst. 



Hydatids have been observed in man, in the ox, 

 in the sheep, in the pig, in the monkey, and other 

 animals which feed usually upon vegetables. They 

 are almost, if not always, absent in carnivorous and 

 in rodent animals, in birds, reptiles, and fishes. 



The hydatid-echinococci probably form several 

 species, but the points of difference which have been 

 observed, either in the hydatids found in man and in 

 animals, or in their echinococci, are not sufiiciently 

 great nor sufficiently precise to constitute distinct 

 specific characters. 



