History of Annual Plagues. 349 



buyer as affords the best assurance possible that the beast has not taken 

 the infection, nor is likely to convey the contagion by any infectious 

 matter adhering to its skin, though not affecting itself, from any diseased 

 beasts it may have approached to others which may come near it. This 

 j)eriod of forty days is allotted because such a certificate could not be 

 made by the owner unless the beast had been long enough in his pos- 

 session to show it had not been infected before it came into his hands, 

 and to afford time for the infectious matter, if any had been contracted 

 by its skin, to have lost its virtue or been worn off, and because it was pre- 

 sumed a less space of time would not have been fully sutHcient for this 

 effect. As to what respects the having actually received infection, forty 

 days' possession is much longer than is needful to manifest whether or 

 no such infection was taken by the beast before became into the seller's 

 hands, since the symptoms would have shown themselves, and the beast 

 would have died of or recovered from the disease long before half that 

 time was expired.' As to what respects the contagious matter that 

 may be contracted by the skin of the beast from others infected, the 

 time in which such matter may lose its contagious power, or the skin 

 become free from it, cannot possibly be ascertained, and there is 

 reason to believe it might go much beyond forty days, but there are 

 easy means to be employed of taking away the hazard of conveying 

 the disease to other beasts in that way, with far greater certainty than 

 can result from the waiting even a much longer space than forty 

 days without the use of such means. 



' The time in which the symptoms appear to come on in the murrain 

 after the taking the infection is, as we have above observed, almost 

 generally on or before the tifth day.^ But as there may be, though 



' It appears, from the experiments made at Utrecht in 1769, as above mentioned, 

 and from others, of the inoculation of the cattle for the murrain, that the longest 

 period in the case of beasts so treated betwixt their receiving the infection and their 

 death was not more than fourteen days. The observations on the same period, 

 with relation to such beasts as have taken the disease from others without inocu- 

 lation where it could be ascertained by the known time of their coming within the 

 reach of the infection, show the longest extent of it in such cases to be about seven- 

 teen days. But this must be understood to be according to the course of the disease 

 in Holland. For in our country the death of the beasts taking the disease naturally 

 was found to happen almost always within twelve or thirteen days after the infec- 

 tion, the crisis or turn of it, as we remarked before, being about four or five days 

 earlier here than in the United Provinces. It must be comprehended, also, that 

 this period of death regards beasts which are carried off by the murrain, considered 

 as an acute disease ; for where they die, after their recovery from the proiicr symp- 

 toms of the distemper, of ulcers or abscesses in the viscera produced by it, no 

 regular period can be fixed on, as those accidents or their consequences differ in 

 every subject where they happen. 



" There is a remarkable uniformity in the operation of the contagion of the 



