^^o History of Animal Plagues. 



rarely, a variation that requires some latitude, we may rate the longest 

 time to be the seventh day. In a very few beasts, however, which 

 have the disease in the most mild and gentle manner, we may also allow 

 time for the aggravation of the symptoms, till they become strong enough 

 to be so clearly perceptible as to leave no room for doubt, and suppose 

 in those instances they may not be very observable till the tenth day. 

 But this is the utmost concession as to the extension of the time in 

 which the infection can lie concealed without sensible effects, that facts 

 will admit us to make ; and if no appearances of the disease be found at 

 or before that period, it may be very safely concluded the beast had not 

 taken the infection before the commencement of such time. If, never- 

 theless, we should go somewhat further to satisfy all scruples as to the 

 inaccuracy of these observ^ations, and stretch our caution to the utmost 

 that can be deemed reasonable, the keeping the beasts twelve days after 

 they are purchased is fully sufficient to determine with the most 

 positive certainty that they were not infected before such purchase. 

 There cannot be the least reason, therefore, to keep the beasts longer 

 than twelve days before they are sold in order to avoid the hazard of 

 their having received the infection before they came into the hands of 

 the owner. 



' The other more specious reason for restraining the sale of cattle 

 during so long a period has not, at the bottom, a more solid foundation 

 in the reality of foots than the preceding. No precise limits can be 

 assigned to the time that beasts, having the infectious matter of the 

 murrain lodged on their skins in consequence of having come near 

 beasts seized with disease, may communicate it by that means to 

 others. 



murrain as to the time it produces sensible effects when communicated by exterior 

 infection. In the above-mentioned experiment made at Utrecht, twelve cows were 

 put to six others that were inoculated, and kept with them in a confined place from 

 the time of inoculation. The twelve were all seized with a cough and gnashing of 

 their teeth the seventh day after the inoculation of the six, and did not exhibit the 

 least difference in the period of their being affected by the infection, which may be 

 concluded to have been taken five days before, as at that time, though it was but 

 the second day after the operation, febrile symptoms began to appear in some of 

 those inoculated, one of which, indeed, was so weak on the third day that she fell 

 down, and had not strength to rise again. The same uniformity is not in the least 

 found in the inoculated beasts, but in most of them the symptoms come on with 

 much more celerity and violence than in those which have the disease by casual in- 

 fection. Many other facts confirm this observation of the almost constant equality 

 of time in which the visible effects are produced in the cattle which have the mur- 

 rain by natural means, and they leave us no room to suspect that the infection ever 

 lurks after it is taken without revealing itself more than six or seven days, even 

 where its action is the weakest. 



