82 BOARD OF AGRICULTURE. 



The four cases making an entire period of 103 days, which, 

 divided by four, gives 25| days as the average time of incubation. 



The time of incubation could not have averaged more than 

 25 days — l)ut it miglit liave been less, as an animal might not 

 take tiie disease during the first few days of exposure. The 

 Olmstead cattle must have contracted the disease 14 days 

 before the first sickness appeared in this herd, inasmuch as the 

 diseased oxen were removed 14 days before any animal belong- 

 ing to it was sick. The probable time of incubation is from 

 two to three weeks. 



The evidence we have in regard to contagion and incubation, 

 although limited, is perhaps more to be relied upon than that 

 in Europe, where the disease has so extensively prevailed, that 

 there would be more chances for unknown exposures. 



PROPAGATION. 



The mode of propagation is very uncertain. Whether the 

 disease is produced by infection from the saliva, by bringing 

 noses in contact, or by the breath, secretions from the skin 

 or excretions of the body, is quite far from being finally settled. 

 It is difficult to say how long an animal may continue to com- 

 municate the disease ; if he has not done so, it does not follow 

 that he cannot. 



Tlie Doane oxen, that gave the disease to Olmstead's herd, 

 could not have boon exposed much before August 1st. They 

 went into William F. Doane's herd on December 3d, and did 

 not give the disease. Therefore months cover the time of 

 incubation and propagation. But these oxen were never off 

 their feed, and did not appear much sick at any time. And 

 had they not given the disease to Olmstead's herd, and been 

 examined post mortem, they might never have been consid- 

 ered ill. 



Chenery's oxen were ill and apparently recovered, in Novem- 

 ber, 1859. In April, 1860, they stood near three cows in the 

 barn in East Lexington, at Mr. Wellington's, while some hay 

 was being loaded. These three cows were afterwards killed 

 and found sound, July the 11th following. 



Here is all the evidence that we have in regard to the length 

 of time during which an animal can give the disease. It may 

 be taken for what it is worth. 



