"GROUSE DISEASE" STRONGYLOSIS 243 



It may be assumed that both cocks and hens have the same Power of 

 opportunities for obtaining food, and that the quantity and r 

 quality of that food is the same for each, consequently each 

 will be equally liable to infection by the Strongyle worm. 

 Why then do the cocks die in larger numbers than the hens ? 

 Only one answer is possible, and that is, that whereas at this 

 time the power of resistance of the cock is at its lowest, the 

 power of resistance of the hen is at its highest. The fact is 

 sufficiently proved by the comparison of the weights of the 

 sexes, but if further confirmation be required it would be found 

 in the fact that in June as the cock increases in weight so he 

 becomes less liable to disease, whereas the hen, whose weight 

 is on the downward grade, continues to suffer, and sometimes 

 to die, throughout the summer months. 



The fact that the average weight of the cock is slightly on 

 the upward grade during the months of greatest mortality 

 is somewhat misleading, until it be remembered that he is still 

 far below his best condition, and was probably about his worst 

 at the time when he first contracted the infection. 



The reason why cocks do not die in September, nor hens 

 in November, when their respective weights are again at their 

 lowest, is obvious mere loss of condition is not enough to cause 

 death. It is only where this loss of condition is found in con- 

 junction with a heavy infection of parasites that it becomes a 

 source of serious danger. 



The reason why the cock bird should be improving in con- 

 dition in June, while the hen bird should be falling off, has 

 already been discussed, 1 and it is only necessary here to repeat 

 that in March and April the cock is subjected to the strain 

 of breeding and moulting, and is recovering in May and June, 

 whereas the hen does not begin to feel the corresponding strain 

 until June and July. This probably also accounts for the fact 

 that cocks die in larger numbers from " Grouse Disease " than 

 hens, for at the time when the nematode infection is at its 

 height the cock is more vulnerable than the hen. 



1 Vide chap. i. pp. 33 et seq. 



