DEVELOPMENT OF HYDATIDS 



249 



vesicles or brood capsules, on the inner surface of which in turn 

 there grow a number of little heads or scoleces. Each of the 

 heads has the power ultimately to grow into an adult worm. 

 As there may be a dozen or more of the scolex-bearing brood cap- 



FiG. 95. Diagram of portion of small Echinococcus cyst showing daughter cyst 

 (d.c), brood capsules (br. cap.) and invaginated heads (h.). X about 5. 



sules in a single hydatid, and from six to 30 heads in a single 

 vesicle, the number of heads or scoleces produced may be enor- 

 mous. Sometimes there may be still further multiplication by 

 the development of secondary cysts either inside or outside of 

 the original hydatid which may develop a 

 whole series of scolex-bearing vesicles of 

 their own. 



Sometimes instead of forming the usual 

 large vesicles and secondary vesicles, the 

 growth results in the formation of a great 

 mass of small separate vesicles (Fig. 96), 

 varying in size from a pinhead to a pea, 

 with few and scattered heads. These masses 

 of vesicles, known as " multilocular " cysts, 

 may be six inches or more in diameter; 



,1 , r. J.1 <• ] • -i_ T Fig. 96. Multilocular 



they are most frequently found m the liver. ^^^^ ^^^^^ ^-^^^ ^f ^^^^,^ a 

 Unless surgically removed they usually prove nat. size. (After Ostertag 



r , ^ 1 , from Stiles.) 



fatal sooner or later. 



The fact that the " multilocular " cysts are not found in Ice- 

 land or Australia where the ordinary cysts are so common, and 

 that they occur to the almost total exclusion of the ordinary 

 kinds in some countries, especially in parts of Germany, suggests 

 that they may belong to a different species indistinguishable 

 from E. granulosus in the adult state. 



