THE GROUSE DISEASE chap. 



from the presence of the malady, which owing to 

 various circumstances to be mentioned hereafter is 

 then less conspicuous, and may even be altogether 

 overlooked. 



The fact that year after year in one or another 

 tv<<(ii^-'j part of the country the disease is or becomes 

 epidemic, is in itself strong prima facie evidence 

 that it is an infectious illness ; further, the now well- 

 recognised occurrence of isolated fatal cases of the 

 same illness amongst the grouse in one or another 

 part of a given district during autumn and winter, 

 makes it certain that the disease has become endemic, 

 and is ready, when favouring opportunities offer them- 

 selves, to assume the epidemic character. This is 

 the case with some other acute infectious endemic 

 maladies affecting men and animals which, at certain 

 times of the year and under certain other favouring 

 conditions, assume the epidemic character. Such a 

 change is, however, a slow and gradual development. 

 Take, for instance, Asiatic cholera, endemic in Bengal. 

 It is present in isolated cases all the year round in 

 some part or another of Bengal. During the cold 

 season the number of cases gradually increases ; by 

 the end of the cold season, during the spring and 

 beginning of summer, the cases become so numerous, 

 and the spread of the disease so conspicuous, even 

 outside the endemic area, that the disease possesses 



