212 STUDIES IN INSECT LIFE, ETC. 

 as is mentioned above, have been found in the 

 intestines of grouse and also in their blood, but 

 in no case, so far, has any of these parasites 

 been shown to have a markedly dangerous effect 

 on the bird harbouring it. Some of these para- 

 sites, in fact, occur in perfectly healthy grouse, 

 and apparently are almost innocuous. 



STRONGYLOSIS 



The second disease which the Inquiry found 

 responsible for grouse epizootics observed be- 

 tween 1905 and 1910 is one to which Cobbold 

 drew attention in 1873, though he attempted 

 little in the way of pathological investigation. 

 According to him it is caused by the presence 

 of a round-worm now known as Trichostrongylus 

 pergracilis, in the caeca. We may call the disease 

 " Strongylosis of the grouse." The worms are 

 minute, transparent, very slender, a little less 

 than half an inch in length, and they may exist 

 in enormous numbers, 10,000 occurring in the 

 two caeca of one bird. They are about equally 

 divided between the two blind-guts. We may 

 recall the fact that in the grouse the caeca are of 

 unusual size, and that the digested food is absorbed 

 in these regions of the alimentary canal alone. 



