"GROUSE DISEASE "PATHOLOGY 299 



in August they were met with in moderate numbers in all the birds examined. 

 From the beginning of September to the beginning of February they were 

 absent from all the birds examined with one exception. The relation to 

 season is much less marked in the case of Davainea urogalli, though it 

 occurred in the greatest numbers at the same seasons as Hymenolepis. 



With regard to Trichostrongylus pergracilis it is difficult to come to any 

 definite conclusion as to its seasonal prevalence from our own observations, 

 conducted as they were on diseased birds at one time of year, and on healthy, 

 often hand-reared, birds at another; but it is clear that they do not dis- 

 appear at any season. 



The causes of death in the Grouse are, of course, various. We ourselves 

 have seen pleuro-pneumonia (in a bird long kept in captivity in Cambridge), 

 pericarditis, necrotic patches in the liver, an obscure chronic disease - 



r Summary. 



of the peritoneum, and septic infection from a gangrenous fracture 

 of the wing. On the other hand, the great majority of birds, either picked up 

 dead on the moor, or caught by keepers when weak and unable to fly, have 

 been found to be all more or less in the same condition ; they were wasted, 

 badly infested with Trichostrongylus pergracilis, and often with Davainea 

 urogalli or Hymenolepis microps, or with both. More or less pathological 

 change was seen in the caeca ; the mucous membrane was often reddened, 

 and under the binocular microscope considerable changes were seen, though 

 we did not observe gross ulceration. Sections examined under the higher 

 powers showed chronic inflammatory changes of a serious kind, particularly 

 in the immediate neighbourhood of the worms. 



Birds showing these changes we take to be representative of those suffering 

 from the chronic form of " Grouse Disease." Whether there be also an acute 

 epizootic disease among Grouse we cannot tell. We can only say 

 that, so far as our experience goes, we have not seen it. We have acute 



"Grouse 



never seen pneumonia in the wild bird, and we have never seen any Disease" 



ofosGrvcd 



birds picked up dead when plump and in good condition without 

 finding evidence that they had died of injury. 



We have therefore to discuss the causes of death in the chronic wasting 

 disease, which is observed among Grouse fairly regularly in the spring and 

 to a lesser extent in the autumn, and it is to this we refer when we speak 

 of " Grouse Disease." 



First we must consider the gross intestinal parasites which occur in such 



