No. 4.] CATTLE COMMISSIONERS. 515 



ditions of winter north of the thirty-seventh parallel, with few 

 exceptions, certainly not north of the thirty-eighth. Whenever it 

 is found north of its usual habitat^ it is because it or its parents 

 have been transported there by cattle in the course of traffic. 



The facts that must be borne in mind when considering any out- 

 break in the north, and I might add within the so-called infected 

 territory, are that cattle bearing ticks drop them ; from these, 

 young ticks emerge usually in about six weeks in warm weather ; 

 and that northern cattle usually die in from two to three weeks 

 after they are attacked. While the time of hatching of ticks is 

 delayed by cooler weather of spring or fall, the above epitome is 

 essentially correct. The time, therefore, betiveen infection of ground 

 and the destruction of cattle is from seven to ten weeks. 



The determination that certain cattle have died of Texas fever, 

 — a disease that can only be communicated by their having been 

 in places infected by cattle brought from the permanently (so- 

 called) infected area, — points out the direction in which one must 

 search for the source of the disease, viz., to cars, stock yards, etc. 



By your direction, Mr. Chairman, I have followed up both neg- 

 ative and positive evidence in this connection ; indeed, this has 

 been necessary, for only toward the close of the investigation did 

 the positive evidence present itself. Since the diseased cattle were 

 scattered to farms from the Brighton stock yards, when there was 

 no disease in other cattle with which they mingled, it became evi- 

 dent that they must have contracted it before being separated. 



On looking back at the date concerning the second carload lot, 

 it will be seen that cattle died eight days after they arrived at 

 Brighton ; also that one cow died in nine days after in the first car- 

 load, and three in the third carload within ten days after arrival. 



A reference to the experiments relating to the time of death 

 from the disease after ticks have been placed upon cattle show it 

 to be thirteen days or more. My own investigations have shown 

 that deaths have occurred in outbreaks as soon as eleven days after 

 exposure ; but this is exceptional. In blood inoculation, where 

 blood was transferred from diseased cattle directly to sound, death 

 in one instance alone was unexpectedly produced in eight days ; in 

 another, in nine days. As a rule, the time is about the same as 

 for tick inoculations. It is conceivable, therefore, that the disease 

 might develop within ten days from tick inoculations, but hardly 

 probable. Since the disease broke out in five cases in from eight 

 to ten days after reaching the Brighton yards, infection from those 

 yards is practically excluded. In the absence of positive infection 

 by the proof of southern cattle having been placed in those yards, 

 they must be regarded as uninfected. 



