482 DISEASES OP CATTLE. 



plant, but it belongs to the lowest fomis of the animal kingdom. 

 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 exceed- 

 ingly minute body, probably endowed with motion, and only after it 

 has succeeded in entering the corpuscle does it begin to enlarge. 

 Plate XL VII, figure 4, illustrates an early stage of this blood para- 

 site. The red corpuscle contains a very minute roundish body which 

 is stained blue to bring it into view. The body is, as a rule, situated 

 near the edge of the corpuscle. Figure 5 illustrates an older stage in 

 the growth of the parasite, in fact the largest which has thus far been 

 detected. It will be noticed that 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 j^Vir to 3^VTr 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 result 

 from the destruction of the red corpuscles. This destruction may be 

 extremely rapid or slow. Wlien 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. Wlien the destruction of corpus- 

 cles 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 

 nnd the early part of August. Cases of the mild type occurring 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 calculation 

 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 ont-twentieth of the weight of the body, a 

 rather low estimate. According to experimental determination 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 24 hours. The remains of these corpuscles 

 and the coloring matter in them must be either 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 



