256 THE GROUSE IN HEALTH AND IN DISEASE 



head tend to fall off so that the forepart of the head and the regioii round the bill 

 become almost bald, and the bird presents a very peculiar appearance, owing to the 

 bluish coloration. Leg weakness was present in several cases. 



The plumage of the infected birds is affected in regions other than the head, 

 and the quills are less rigid than in normal birds. The feathering of the legs 

 is ragged, and the sheen on the neck and tail-coverts is not so well developed, 

 while the replacement of nestling down by ordinary feathers is much retarded 

 in diseased birds. 



During the progress of Coccidiosis the birds sometimes develop much mucus 

 and a very offensive " breath," a smell of sulphuretted hydrogen being notice- 

 able. Both sticky mucus and smell disappear as a rule in a few days, but may 

 recur. 



While birds suffering from Coccidiosis feed greedily, internal digestive troubles 

 occur, and the fseces voided by the birds are very fluid, the condition being that of 

 diarrhcea. The caecal droppings are the more noticeable, and they contain many 

 resistant cysts (oocysts) (Figs. 4-8) of C. avium. Both sportsmen and keepers have 

 noted that diarrhoea is a marked symptom of "Grouse Disease." Examination of 

 soft droppings daily shows the relative numbers of oocysts present, and may be a 

 rough gauge of the intensity of the infection.^ In good health the cascal drojjpings 

 are of firm consistency and olive-green to brown in colour. When Coccidiosis is 

 slight, the fgeces become softer and brownish yellow. In acute cases the excrement 

 is almost fluid, and the birds void sulphur-yellow faeces with a heavy, foetid odour. 

 Fatty matters may be present in the cascal contents. 



A day or so before the death of the infected bird the slimy, mucilaginous dis- 

 charge recommences, ooze coming from the beak, nares, ears, and eyes. Examina- 

 tion of this liquid by the microscope shows the presence of oval coccidian oocysts 

 {cf. PI. xxxviii.. Figs. 4-8), all of which show the characteristic cyst- wall within which 

 is a single uninucleate mass of protoplasm. The mucus also contains some shed 

 epithelial cells in which occasionally macro- and micro-gametes may be found. The 

 ooze from the eyes and beak chiefly contains oocysts which may be due to regurgita- 

 tion from the crop just before death. However, it should be noted that while 

 raucous discharge is common, it is not an invariable feature of Coccidiosis. 



Death from Coccidiosis appears to be sudden. Some of the experimental fowl 

 chicks were feeding greedily an hour before death, though death was almost 



' It should be noted that in severe cases of duodenal Coccidiosis, merozoites may be found free in the 

 gut contents and faces of infected birds when no oocysts are present. 



