NATURE OF THE DISEASE 



than under that of parasitism, are chiefly those de- 

 rived from the consideration that the former theory 

 fully comprehends all the conditions which the 

 phenomena of the grouse disease may present ; and 

 further, that the theory may be applied to the ex- 

 planation of points and facts, of which the theory 

 of helminthiasis can take no heed. 



** We thus find that these birds are almost invariably 

 affected by both kinds of entozoa — most specimens 

 to a moderate extent, some to a very great degree. 

 But it is exceedingly rare to meet with a bird in 

 which not a single parasite of either kind is present. 

 Out of many cases examined not a single bird was 

 found actually free from the characteristic tape-worm, 

 and in one or two doubtful instances only could it be 

 asserted or suggested that none of the round worms 

 were present. ' 



" That the presence of these parasites was uncon- 

 nected with the death of the great majority of the 

 birds examined is, I think, proved by the want of 

 any causal or obvious relationship between the infesta- 

 tion and the fatal issue ; and also by the absence, in 

 most cases, of the signs of fatal parasitism — such as 

 inanition, producing the * pining ' condition, actual per- 

 foration, morbid appearance of the muscular tissues, 

 etc. No one can deny that the presence of para- 

 sites in large numbers undoubtedly causes death in a 



cU 



