436 EEPOET OF THE BtJEEAU OF ANIMAL INDUSTEY. 



time. Judging from, a proclamation of the governor of Illinois, 

 issued to take effect the 25th of September, there had been, previous 

 to the latter date, no effective means taken to insure that cattle sus- 

 ceptible to the Southern cattle fever should not come in contact either 

 with affected Southern cattle or with their trail. The shifting of 

 these cattle from pen to pen increased the chances of infection from 

 Southern cattle, thousands of which were weekly passing through the 

 yards. * 



After the 6th of August all the cattle passed through the same 

 conditions, but to what extent they were exposed to any contagion 

 en route from the Chicago to the Calverton drove-yards can not 

 be learned. Their chances of infection ceased after leaving the Cal- 

 verton yards. 



As nearly all died about the same time, it may be urged that they 

 must have contracted the disease after being collected into one herd, 

 for it is generally believed that one native cow can not take it from 

 another. The subsequent history of the outbreak shows, however, 

 that these sick animals did give the disease to at least eight native 

 cows, under conditions far more unfavorable than those presented 

 by the animals transported and driven together in a close drove. 

 There is no reason to suppose, therefore, that this disease may not 

 have spread while the cattle were en route. 



The time, then, during which I .consider that the herd was ex- 

 posed was about a week, or from a day or two before the 6th until 

 the 10th of August. It should be borne in mind, however, that, 

 though there were increased probabilities of infection at cer- 

 tain points, it would be unjust to say that it did occur in any par- 

 ticular place until the weight of the circumstantial evidence bears 

 out the assertion. Also that a single hour's exposure to the trail 

 of infected cattle at any point along the route would -have been 

 sufficient to infect the herd. From the time that the animals 

 were exposed until they began to show signs of the disease was the 

 period in which the disease was incubating or developing. Each of 

 the farmers stated that they did not notice that the cattle were sick 

 until two or three days before they died. - This stage extended from 

 the 10th to the 20th, when one or two were noticed to be ill, or until 

 the 24th, when more showed symptoms. The duration of this stage 

 was therefore about two weeks. It covered a part or all of the time 

 that the cattle were in transit from Chicago to Calverton, and the 

 time until after the cattle were distributed to the farms on which 

 they died. During the first part of this period the cattle were neces- 

 sarily restless, excited, and over-heated, on account of the transpor- 

 tation. During the latter part they were only subject to such dis- 

 turbances as would accompany their becoming accustomed to a new 

 place. 



The stage of manifest fever succeeded, and although it occupied 

 but two or three days for each animal, yet for the herd collectively 

 it extended from the 21st of August to the 4th of September, and for 

 the herd can be considered as embracing about a week and a half. 

 For about 70 per cent, of those that died this stage was comprised 

 within a week. 



* The already of fc-repeated experiment of allowing native cattle to live on the 

 trail of Texas cattle, which was initiated on the 3d of July in the Chicago stock- 

 yards, by placing five cows in pens frequented by Texas cattle, with the resulting 

 illness of all and the death of four from the Southern cattle fever, is sufficient of 

 itself to indicate that infection in these yards was quite possible. 



