THE BEGINNING OF INFECTION 121 



for such organisms prior to that of Coccidium, 

 but coccidiosis is the name established for the 

 disease. As before mentioned, the faeces of birds 

 suffering from coccidiosis contain numerous oval 

 shining bodies. Each is about T J^ the size of a 

 grain of wheat, and possesses a very tough, resistant 

 coat. These bodies are known as oocysts, or, more 

 popularly, cysts. After a short time, under favour- 

 able conditions of warmth and moisture, four other 

 oval bodies, each with its own resistant coat or 

 sporocyst, develop within the oocyst (Fig. 28, S). 

 Each of these is a spore, and ultimately within the 

 spore two primary infecting germs, or sporozoites 

 (Figs. 27, spz. ; 28, A) t are produced, the broad end 

 of the one lying near the narrow end of the other. 



The faeces crumble into dust, and, carried by the 

 wind, the oocysts find their way to the pools or tarns 

 at which the grouse drink. When the wind drops, 

 they are deposited as fine dust in the water or on the 

 tender shoots of the heather that is the diet preferred 

 by the bird. The contamination of the drinking- 

 water also is aided by the rain washing excrement 

 into the pools. When the cysts are taken up with 

 the food or drink of their host, they resist the crush- 

 ing by the gizzard and the action of the digestive 

 juices until they are passed into the duodenum. 

 Here a very different state of affairs occurs. Under 

 the powerful action of the pancreatic juice poured into 

 the first part of the gut the duodenum aided by 

 the increase in temperature,, the tough cyst walls are 

 softened, and the sporocysts partly or entirely escape, 

 only to be softened in their turn. The two sporo- 



