690 INFECTION AND IMMUNITY. 



cooked vegetables in regions in which the disease 

 is endemic, as in the Philippine Islands. 

 immunity. From the fact that foreigners going into tropical 

 countries are more susceptible to infection than the 

 natives, it is concluded that the latter have some 

 natural (or acquired) immunity to the disease. 

 Children are said to be less susceptible than adults 

 and in them the disease yields to treatment more 

 easily. There is no serum therapy for the infec- 

 tions. The salts of quinin in strengths of from 

 1-1500 to 1-750 are amebicidal when injected into 

 the colon. 



V. SARCOSPORIDIA. 



Sarcosporidia are unicellular parasites which are 

 found within the muscle cells of some animals,, but 

 very rarely in man. They are more or less tubular 

 or oval in shape and are frequently referred to as 

 Miescher's tubules. Their size varies greatly and 

 certain species may reach a length of two centi- 

 meters. When well developed they possess two 

 capsules a dense outer capsule, which is perfor- 

 ated with minute canals (?) directed toward the 

 center of the parasite, and an inner thin hyalin 

 membrane. Both represent differentiated ecto- 

 plasm (Doflein). The endoplasm, even in young 

 cells, gives rise to numerous small nucleated 

 spheres (pansporoblasts), which increase in size 

 and each of which eventually becomes multinu- 

 cleated and forms numerous kidney or sickle- 

 shaped, nucleated sporoblasts. Each sporoblast 

 finally gives rise or is changed into a well-charac- 

 terized spore with a membrane and a nucleus. 

 This process takes place first in the central part 

 of the parasite, but eventually extends to the ends 



