74 Diseases of I'miltri/ 



tract (4a) and each one penetrates with its pointed end an 

 epithelial cell of the intestine as at 5. In the figure 5a, 

 56, 5c, 6 and 6a, represent the succeeding stages of growth 

 of the organism within the intestinal cell. As shown in 

 6a and 7, the parasite grows so large that it completely fills 

 the cell. Finally these cells are broken down and torn off 

 the intestinal wall. The stage of the parasite shown at 6a 

 and 7 is known as the schizont. The next step is for the 

 schizont to break up into a larger number of sharp pointed 

 bodies as shown at 7a. These escape and enter other epi- 

 thelial cells just as the somewhat similar bodies did at 5. 

 At this point the organism may do one of two things. The 

 small sporozoids from 7a may develop exactly as the 

 sporozoids did from 5 to 7. This part of the life cycle, as 

 shown by the shorter arrow from 7a to 5, may be repeated 

 any number of times. 



If, however, the conditions are not very good, i.e., the 

 bird is about to die, the sporozoids undergo an entirely dif- 

 ferent development, as shown at numbers 7 to 15 (Fig. 8). 

 Here the sporozoids enter the epithelial cells and some de- 

 velop into very large (egg) cells (female element), as shown in 

 <Sa. Others, 9a and 10a, form a very large number of minute 

 motile zooids or sperms (male element) which unite with 

 one or more of the large egg cells as shown at 11. After 

 this sexual union there is developed the oocyst like No. 1, 

 with which we started. At all stages of this disease many 

 of these cysts are carried to the outside with the feces 

 and upon being picked up serve to infect other birds. 

 Death is caused by the parasite attacking so many of 

 the intestinal cells that the bird is no longer able to digest 

 its food. 



Other species of coccidia have different life cycles. Some 

 are simpler and some more complex than the example 

 given above. 



