114 THE GROUSE IN HEALTH AND IN DISEASE 



" Granting as I do that this nasty little parasite Strongylus 

 does occasion disease in Grouse, is there anything illogical in 

 attributing the cause of the worm to the bird being compelled 

 to eat unwholesome food, from its natural food the heather 

 being damaged or destroyed from continued blighting east 

 wind ? And thus the blight of the heather is really at least 

 one cause of ' Grouse Disease.' ' 



" Insufficient or unwholesome food is the cause at least of 

 one type of disease amongst Grouse." 



Or the following : 



" ' Grouse Disease ' is caused mainly by overstocking, over- 

 preservation, and the complete and indiscriminate slaughter of 

 certain species of so-called vermin, notably the Peregrine Falcon ; 

 also by the state of the young and old heather after severe and 

 late frosts which do much more harm now that heather-burning 

 is done systematically. Also by greed for big stock. Unnatural 

 and rapid burning of heather and a wholly artificial state of 

 Grouse farming ; also interbreeding." 



In the above quotations, which may be perfectly sound so 

 far as they go, we have a very fair summary of possible pre- 

 disposing causes ; but the immediate cause of " Grouse Disease," 

 whether we consider the disease to be Pneumonia, or Strongy- 

 losis, or Coccidiosis, or Enteritis, or any other sickness in the 

 world, is not touched. 



Until, therefore, we have discovered the active agent in a 

 disease we cannot say that we know its cause. This is a funda- 

 mental rule, and to be satisfied with predisposing causes is to 

 be satisfied with less than half the truth, though that half is, 

 of course, very important if our intention is to proceed further 

 in the attempt to discover a remedy for the disease in question. 



The primary or acting cause of Klein's acute infectious 

 pneumonia was believed to be a bacillus known as the Bacillus 

 coli ; the primary cause of Cobbold's Strongylosis is the thread- 

 worm Trichostrongylus pergracilis ; the primary cause of Grouse 

 Coccidiosis is Eimeria (Coccidium) avium, and so on ; not east 

 winds or the absence of the Peregrine Falcon, 



