EEPOKT OF THE BUREAU OF ANIMAL INDUSTRY. 437 



This stage was abruptly terminated by death, in 85 per cent, of the 

 original herd of cattle taken to Union ville not an extremely high 

 percentage of fatality to be caused by this disease, but very high 

 when compared with that caused by other contagious diseases of 

 cattle in this country. The remaining 15 per cent, were, on the 9th day 

 of September, convalescing, but the most of them appeared to have 

 been very sick and as though they had small chances of recovering. 

 The table (I) shows that this stage had reached its maximum on the 

 28th of August and fell rapidly off, there being after this but two 

 deaths a day, excepting the 30th, when there were five. This scatter- 

 ing of the fatality seems to indicate that these animals were perhaps 

 better able to resist the disease than those stricken down earlier. In 

 the cases of introduced cattle that I was able to examine there 

 seemed to be a more chronic form of the disease than existed in the 

 single native cow that I examined; that is, the animals dying in 

 these later days had passed through the acute stages and were enter- 

 ing into the chronic stages of the disease. 



These stages of the disease may be roughly reviewed in the follow- 

 ing table, which considers the disease of the herd and not of indi- 

 viduals: 



TABLE II. 



Stage of infection, one week. 

 Stage of incubation, two weeks, 

 Stage of fever, two weeks. 



For the individuals affected, the following table will more nearly 

 represent the truth: 



TABLE III. 



Exposed to infection, part or all of seven days. 

 Stage of incubation, thirteen to twenty-five days. 

 Stage of fever, two to three days. 



As the exact date of exposure can not be learned, these dates are 

 only approximate. It is not likely that all of the cattle could have 

 had the disease before being brought together in Chicago; so that it 

 is fair to assume that the whole course of the outbreak was com- 

 prised within from four to five weeks. The death of the animals 

 occurring as early as fifteen days, and the destruction of the bulk of 

 the herd within twenty days, after the herd was made up, indicate 

 that the outbreak was . one of the virulent type. In this outbreak 

 the period of thirteen to twenty days is necessarily as long as the 

 period of incubation of the greater proportion of the diseased cattle, 

 for they were collected on the 6th of August, separated on the 13th, 

 and had nearly all died by the 28th. The period of exposure for at 

 least part of the animals, if not all, supposing that all had not been 

 infected before the herd was made up, was from the 6th to the 13th 

 of August, the dates between which all of these animals were more 

 or less intermingled, or seven days. The total duration of the out- 

 break was about five weeks, or thirty-five days. 



THE DISEASE AMONG NATIVE CATTLE. 



At the time of this outbreak eight native cows died under such cir- 

 cumstances as to justify the assertion that they died of the Southern 

 cattle fever. They belonged to William Baker, James Etzler, George 

 Norris, and Long & Boston. These animals were infected under a 



