DISEASES OF HORSES AND CATTLE. 347 



iieifers before calving. It is chiefly seen in cows 

 from four to six years of age. Mr. Ceely makes the 

 following sensible remarks on the cause and ori- 

 gin of this disease. Referring particularly to the 

 Vale of Aylesbury he says: "The variola vac- 

 cine seems to have been long known in the Yale 

 and neighborhood. They have been noticed at 

 irregular intervals, most commonly appearing 

 about the beginning or end of spring, rarely dur- 

 ing the height of summer, but I have seen them 

 at all periods from August to May and the be- 

 ginning of June. By some it is presumed that cold 

 and moisture favors their development, by others 

 that the hard winds of spring after a wet winter 

 are supposed to have the same influence. I have, 

 however, seen the disease in the autumn and mid- 

 dle of winter after a dry summer. The disease is 

 occasionally epizootic or prevalent at the same 

 time in several farms at no great distance; more 

 commonly sporadic or nearly solitary. It may be 

 seen sometimes at several contiguous farms; at 

 other times one or two farms apparently under 

 like circumstances of soil, situation, etc., amidst 

 the prevailing disease entirely escape its visi- 

 tations. Many years may elapse before it recurs 

 at a given farm or vicinity, although all the ani- 

 mals may have been changed in the meantime. 

 I have known it to occur twice in five years in a 

 particular vicinity and at two contiguous farms, 

 Avhile at a third adjoining dairy, in all respects 

 similar in local and other circumstances, it had 

 not been known to exist for forty years. It is 



