376 THE GROUSE IN HEALTH AND IN DISEASE 



any but the sharpest grits, the encysted Strongyles pass once more into the 

 caecum, and on the third day reach the adult stage ; the females become fertile, 

 and three days later the myriad offspring set forth once more to infect 

 the moor. 



It is only when the adult Strongyle is found in the caecum in large numbers 

 that the health of the Grouse is appreciably affected. If we consider that birds 

 may be packed in large numbers on one portion of the feeding area, for perhaps 

 weeks at a time, herded together by stress of weather or shortage of food, that 

 the number of Strongyles will increase by geometrical progression as the birds 

 get more heavily infected, and therefore increasingly able to foul the moor, 

 it is not difficult to realise, despite the countless thousands of larvae destroyed 

 by drought, mishap, heather-burning, etc., how the moor may become more 

 and more tainted, until at last every shoot of heather bears the seeds of 

 " Grouse Disease." 



Equal in importance to the presence or absence of the Strongyle is the second 



factor, the power of resistance of the individual Grouse. The fact that the 



normal Grouse, in the proportion of ninety-five to five, has its cseca 



resistance charged with Strongyle worms shows that, under a certain set of natural 



of Grouse. . 



conditions, the worms are not necessarily hurtful to their host. Upset 

 the natural balance, and this at once ceases to be the case. 



This varying power of resistance of the host to parasitic or bacterial 

 infection has long been a recognised commonplace of science. 



Recent scientific investigation seems to indicate that the power of resistance 

 varies directly with the health of the subject, and as far as the Committee's 

 investigation goes, the Grouse appears to be no exception to the rule. A bird 

 in full health, weight, and plumage can carry his quota of Strongyles like an 

 alderman his wine ; but once allow the vitality or weight to go below a certain 

 recognised figure, then immediately the Strongyle worm appears to operate on 

 the tissues of the lining of the caeca. The caeca become inflamed, the digestive 

 process is no longer effective, the moult is delayed so that the bird loses the 

 fresh colour of its plumage, it declines in weight, and, after a more or less 

 protracted resistance, eventually succumbs. 



Without going into the whole argument in support of this theory it is only 

 necessary to say that the weight of the bird is the most easily recognised 

 indication of its power of resistance to disease. That nine-tenths, if not all, of the 

 outbreaks of " Grouse Disease " have their origin in the spring, when the food- 



