374 THE GROUSE IN HEALTH AND IN DISEASE 



doses are sufficiently often repeated, the bird can be done to death with all the 

 recognised symptoms of true " Grouse Disease." 



In addition to the examination of the caeca or blind guts of diseased birds 

 the Committee have paid very close attention to the intestines of healthy birds, 

 with the result that over 95 per cent, of the birds examined have proved to be 

 infected with the Strongyle worm ; that is to say, that almost every bird on 

 a moor contains in its body under normal conditions the immediate cause of 

 " Grouse Disease," and is to a greater or less extent an agent for the dissemina- 

 tion of that scourge. 



If we admit the truth of these statements, and close perusal of the preceding 

 chapter will make it difficult not to do so, we see at once that we have in the 

 Grouse, not a bird free from all the ills that flesh is heir to, struck down in its 

 thousands at no infrequent intervals when the gods are unkind, but rather an un- 

 fortunate moor-fowl, carrying in its body an inherent liability to disease which only 

 requires certain specified conditions to develop and turn the hardiest of all game 

 birds into a badly-feathered, rusty piner, scarcely able to fly, and ripe for death. 



What the conditions are that make this latent and endemic evil assume 

 an epidemic or partly epidemic form is a subject which is all - important to 

 moor-owners, and on the correct definition and diagnosis of these conditions 

 the health of the moor directly depends. 



Briefly put, we have two factors common to all epidemic diseases, the 

 always present, occasionally harmful intruder, and the host ; that is to say 

 the Grouse, at times successfully resistant, at times pathologically affected by 

 the nematode worm. In examining the action of these two variant factors 

 from the point of view of the moor-manager, all that is necessary to ascertain 

 is (1) with regard to the Strongyle what are the predisposing causes which 

 affect its occurrence in the Grouse's caeca, in greater or less numbers with 

 more or less harmful consequences ? And (2) with regard to the Grouse 

 what are the predisposing conditions that tend to raise or lower the bird's 

 power of resistance to the ever-present evil ? 



If we can get a clear conception of these two sets of contributory causes 

 we can proceed with some confidence to investigate measures put forward for 

 the improvement of the health of moors. 



Life history Before considering the conditions affecting the degree of infection 

 Strongyle of birds by the Strongyle worm, it is necessary to refer to the life 

 history of the parasite itself. 



