colle) is allied to a form which lives in the human 

 appendix, and at times is the cause of appendi- 

 citis. 



Beside the worms we have in the grouse seven 

 distinct unicellular or protozoan parasites 

 which live in the intestines or in the blood of 

 the grouse. Most of these are uncommon and 

 comparatively harmless, but one, a Coccidium 

 (there is no more popular word for it), is the 

 cause of disease in the grouse chicks. 



The disease we may call it Coccidiosis for 

 short caused by this species of Coccidium 

 (Eimeria avium) is brought about in this way. 

 The grouse moor is simply peppered over with 

 millions of oval cysts, or capsules, which 

 represent the free-living stage in the life history 

 of the Coccidium. Each cyst is very resistant 

 to changes of temperature and moisture, and 

 can live for a long time. The cysts pass with 

 the food or the water or the grit into the ali- 

 mentary canal of the bird, and in the duodenum 

 the thick cyst wall is dissolved and four spores 

 emerge. Each of these spores enters one of 

 the cells lining this part of the intestine and 

 destroys it. Now, when one reflects on the 

 thousands of cysts which are at times taken 

 up by the grouse, one can readily understand 

 that the presence of these spores boring into 

 the epithelial cells ultimately destroys the 

 lining of the duodenum, where in fact the most 

 active digestive processes are carried on in the 

 normal bird. Furthermore, the Coccidia 

 multiply in the intestine, and the resulting 

 progeny attack new regions of the alimentary 

 tract, especially the caeca. After a time some 

 of them produce small forms (males), and 

 others change into large forms (females) ; 

 these two forms fuse, and the resulting stage 



