252 THE GROUSE IN HEALTH AND IN DISEASE 



Part II. — Experimental Studies on Avian Coccidiosis, especially in 

 Relation to Yoong Grouse, Fowls, and Pigeons. 



I. Introduction. 



Protozoal parasites are highly specialised animalcules which live in intimate 

 relation with the hosts they infect. While many of the protozoa are capable of 

 living in one host only, there are others which are under suspicion of infectiilg 

 several species of higher organisms as host, and of not being so limited to one host 

 as was formerly believed. One test for the specificity of any protozoal parasite is 

 that it fails to develop in any animal other than its special, natural host, and 

 merely perishes when inoculated or otherwise introduced into any other animal. In 

 order to test the specificity of the coccidian parasite of the Grouse, experiments 

 were made, with the result that the Coccidium pathogenic to young Grouse and 

 responsible for the dwindling of the broods, particularly in the spring and early 

 summer, was found to be equally injurious to healthy young fowls and young 

 pigeons. Healthy Grouse chicks also were experimentally treated by administering 

 food mixed with small quantities of infected feeces from other Grouse suffering from 

 Coccidiosis, and fatal results ensued. 



The results set forth in this Memoir are those obtained from one season's work 

 only, to which my investigations were limited. 



II. Experimental Methods. 



The birds used in experimental Coccidiosis were Grouse chicks, fowl chicks and 

 young pigeons, all of which were initially healthy. Coccidian oocysts (PI. xxxvni., 

 Figs. 4, 5) contained in cfecal droppings from infected Grouse were allowed to 

 develop spores to some extent by being thinly spread in Petri dishes and covered 

 in order to prevent complete drying. Under these conditions the spores 

 (Figs. 6, 7) developed in two to three days at summer temperature. The ffeces 

 so prepared were then administered to the healthy young birils. 



(A) Gronse Chicks. — As these birds are somewhat wild, even though bred in 

 captivity, a rapid feeding method was adopted. Some of the partly dried fa'cal 

 matter was taken up on a spatula and inserted directly into the mouth of the bird. 

 Rather large quantities were given as first doses, but if infection was not fairly 

 rapidly brought about the dose was repeated. The c?ecal droppings of treated 



