168 TREATMENT PROPHYLACTIC. 



the liver, says we are acquainted with no prophylactic 

 measures for preventing the entrance of the " Tamia 

 echinococcus " into the system, because the manner in 

 which this is effected has hitherto eluded all investiga- 

 tion. Hence medical treatment can only be directed 

 against the hydatids already developed." Let us see : 

 " Prevention," it is said, is better than cure. Now I 

 have already pointed out that the essential cause of the 

 formation of the echinococci is the swallowing of the 

 ova or embryo of the " Tsenia echinococcus," which 

 pass from the stomach into the duodenum, and from 

 thence into the liver. Accurate observation is, however, 

 wanting as to the manner in which this is accomplished ; 

 all we at present know is, that they are met with in 

 large numbers in the liver, as well as other parts of the 

 body. As a general proposition, it is inferred that the 

 animal infested by cystic worms is usually the source 

 of food, or the prey, of that infested by tapeworms. 

 The host of the cystic worm is devoured by a carnivo- 

 rous predaceous animal, and by this means the cystic 

 worm arrives, together with his host, in the stomach of 

 the carnivorous animal. During the process of diges- 

 tion, the enveloping cysts in which the cystic worms 

 were enclosed are digested, or opened by the teeth of 

 their devourer, when the cystic worm escapes into the 

 cavity of the stomach, and thence to other organs 

 of the body, either by migration, or may be by absorp- 

 tion, via the lacteals and thoracic duct into the general 

 circulation. For our present purpose it is sufficient to 

 know that the OVA of the "Taenia echinococcus" develop 

 hydatids in many animals besides man namely, the 

 sheep, dog, lamb, rabbit, rat, and mouse; and who 



