" GROUSE DISEASE " STRONGYLOSIS 221 



in the diseased birds, much larger indeed than those found in 

 all but the exceptional members of the healthy class, and these, 

 for reasons just stated, may perhaps not be normal at all but 

 suffering from the early stages of " Grouse Disease." 



These nematodes, in birds picked up dead or sent for examina- 

 tion as suffering from " Grouse Disease," are almost always 

 associated with grave changes in the lining membrane of the 

 caecum. Concurrently with these changes intestinal bacteria, 

 particularly those belonging to the Bacillus coli group, find their 

 way into the liver, or even into other organs, but no direct 

 injury can be traced to the presence of these intestinal bacteria. 



" Grouse Disease," then, does not appear to be a specific 

 bacterial infection. It would seem that all the birds which 

 are more or less severely affected by Strongyles suffer direct 

 injury to the caeca to an extent which is more or less proportional 

 to the severity of the infection. Some exceptionally strong 

 birds may stand a larger infection better than weaker birds 

 will stand a lesser ; but, on the whole, the birds with the largest 

 numbers of Strongyles suffer most. Their nutrition is impaired 

 owing to interference with the normal absorption of digested 

 food, and to the abnormal absorption of soluble poisons and 

 intestinal bacteria. Such birds become the weakest ; and when 

 food is scarce, as it is at the beginning of spring, especially after 

 bad winters or on overstocked moors, or when other harmful 

 influences prevail, it is the weakest birds which suffer most. 

 They die of Strongylosis acting on a constitution already 

 weakened by the consequences of privation, while their stronger 

 neighbours manage to pick up a living somehow, and so tide 

 over the period of distress. 







PART II. LIFE HISTORY OF TRICHOSTRONGYLUS PERGRACILIS 



In view of conclusive evidence accumulated by the Inquiry 

 regarding the constant presence of the Trichostrongylus pergracilis 

 in the caeca of nearly all sick adult Grouse, it became a matter 

 of importance to study in some detail the life - history of this 



