DISEASES OF CATTLE 319 



disease has played a very important part in determining the methods 

 that should be adopted in preventing its spread. It established an 

 essential point and indicated many lines of investigation which have 

 yielded and are still likely to yield very important results. 



Nature of the Disease. Texas fever is caused by an organism 

 which lives within the red-blood corpuscles and breaks them up. It 

 is therefore simply a blood disease. The organism does not belong 

 to the bacteria but to the protozoa. It is not, in other words, a micro- 

 scopic plant, but it belongs to the lowest forms of the animal king- 

 dom. This very minute organism multiplies very rapidly in the 

 body of the infected animal, and in acute cases causes an enormous 

 destruction of red corpuscles in a few days. How it gets into the red 

 corpuscle it is not possible to state, but it appears that it enters as an 

 exceedingly minute body, probably endowed with motion, and only 

 after it has succeeded in entering the corpuscle does it begin to en- 

 large. The body is, as a rule, situated near the edge of the corpuscle. 

 There are usually two bodies in a corpuscle. These bodies are in 

 general pear-shaped. The narrow ends are always toward each other 

 when two are present in the same corpuscle. If we bear in mind that 

 the average diameter of the red-blood corpuscles of cattle is from 

 1/4000 to 1/5000 inch, the size of the contained parasite may be at 

 once appreciated by a glance at the figures referred to. 



The various disease processes which go on in Texas fever, and 

 which we may observe by examining the organs after death, all re- 

 sult from the destruction of the red corpuscles. This destruction 

 may be extremely rapid or slow. When it is rapid we have the acute, 

 usually fatal, type of Texas fever, which is always witnessed in the 

 height of the Texas-fever season ; that is, during the latter weeks of 

 August and the early weeks of September. When the destruction of 

 corpuscles is slower, a mild, usually nonfatal, type of the disease is 

 called forth, which is only witnessed late in autumn or more rarely 

 in July and the early part of August. Cases of the mild type occur- 

 ring thus early usually become acute later on and terminate fatally. 



The acute disease is fatal in most cases, and the fatality is due 

 not so much to the loss of blood corpuscles as to the difficulty which 

 the organs have in getting rid of the waste products arising from 

 this wholesale destruction. How great this may be a simple calcu- 

 lation will serve to illustrate. If we take a steer weighing 1,000 

 pounds, the blood in its body will amount to about 50 pounds, if we 

 assume that the blood represents one-twentieth of the weight of the 

 body, a rather low estimate. According to experimental determina- 

 tion at the Bureau Station, which consists in counting the number of 

 blood corpuscles in a given quantity of blood from day to day in such 

 an animal, the corpuscles contained in from 5 to 10 pounds of blood 

 may be destroyed within twenty-four hours. The remains of these 

 corpuscles and the coloring matter in them must either be converted 

 into bile or excreted unchanged. The result of this effort on the part 

 of the liver causes extensive disease of this organ. The bile secreted 

 by the liver cells contains so much solid material that it stagnates 

 in the finest bile canals and chokes these up completely. This in 



