AND IN EPIDEMICS. 69 



It also acts only at night, or until the dew has been ex- 

 haled from the grass in the morning; for even the worst 

 ranges are safe during the day, except where they lie in 

 thickly wooded districts. 



This disease has been found in rich alluvial places, on 

 high barren ridges, on open plains, and in the deepest 

 woods. Its place is sometimes confined to a small space 

 inclosed as a " sugar-orchard," and entirely destitute of 

 water; while it extends in other cases throughout a long 

 narrow range of country, for as much as one hundred 

 miles. 



From the testimony of authors, each of whom has a pe- 

 culiar opinion on the point, milk-sickness may prevail in 

 wet or dry, hot or cool autumns, the character of the sea- 

 son seeming to have no especial relation to the severity of 

 the epizootic. 



The period of incubation varies in cattle, from two to 

 ten days, when an attack is not sooner excited by violent 

 exercise. When the disease is produced by the swallowing 

 of poisonous beef, or milk, butter or cheese, the nausea and 

 vomiting may occur almost instantaneously, or may not 

 appear until after the lapse of several hours or even days. 



"Whatever may be the poison, it seems, according to the 

 experiments of Graaf, to be reproductive within the sys- 

 tem of the poisoned anitnals; for, the quantity of flesh ne- 

 cessary to produce the diseased effect, was about the same, 

 whether taken from an animal originally affected, or from 

 others successively poisoned by its flesh or milk. 



Most writers say, that attempts to inoculate with the 

 blood, milk, &c., of affected animals have failed, but Drake 

 asserts, on the authority of two credible witnesses, that 

 the milk-sickness was produced in them by skinning dis- 

 eased cows. 



