DISEASES OF CATTLE 35 



many of these organisms frequently find their way into the animal 

 body and produce disease. It is also well known that these micro- 

 organisms, or germs, vary in form and other characteristics and that 

 for each disease of an infectious nature there is a specific germ. 



If these germs could be confined to the animal body and die 

 with it there would be no such thing as an infectious disease. Un- 

 fortunately, however, they are thrown off by the animal through the 

 excretions and lie in the earth, in the litter of stables, upon the floor 

 and walls, and in cracks and crevices. Here they may remain and 

 maintain their virulence for an indefinite period, ready at any time 

 to Be gathered up by an animal in its feed or to be blown about in 

 dust and drawn into the lungs. 



For example, we have tuberculosis in cattle and glanders in the 

 horse. In the former disease the causative agent is a rod-shaped 

 germ (Bacillus tuberculosis), which is about one-thousandth of an 

 inch in length. Cattle affected with tuberculosis pass myriads of 

 these germs with the manure, and it is not difficult to understand 

 how in the average stable they would have little difficulty in finding 

 many lodging places. In glanders the causative agent is another 

 rod-shaped germ (Bacillus mallei), about the same length as the 

 tuberculosis germ, but somewhat thicker. A characteristic of this 

 disease is the formation of ulcers in the nostrils and other portions 

 of the body, from which there is more or less discharge laden with 

 the glanders germ. And here, again, it is not difficult to understand 

 how one diseased animal may contaminate extensive premises. 



As has been stated, some of these minute forms are vegetable or- 

 ganisms. In fact, these vegetable parasites are the cause of some of 

 the most destructive diseases, and some of them are very difficult to 

 destroy, for the reason that they contain spores. A spore may be 

 likened to the seed of a plant, for it bears about the same relation to 

 the bacillus that a grain of wheat does to the plant proper. As the 

 plant may be destroyed and the seed remain latent for an indefintie 

 time, so destruction of the bacillus may be easily accomplished while 

 the spores remain unharmed and retain life for weeks or months. 



An example of this class of organisms is seen in the agent 

 which causes anthrax (Bacillus anthracis). Ordinary methods for 

 the destruction of the bacillus will not destroy the spore as well, and 

 thus anthrax becomes a most difficult disease to eradicate. Upon 

 farms where animals have died from anthrax and the carcasses have 

 been buried instead of destroyed, repeated outbreaks of the disease 

 may occur from time to time, possibly extending over a period of sev- 

 eral years. This condition is due to the existence of the very resistant 

 spores, which under favorable circumstances are carried to the sur- 

 face of the earth and become infecting organisms much as the seed 

 of a noxious weed, after remaining in the soil during the winter, 

 finds the conditions favorable in the spring and develops into a plant 

 except that these minute forms of life multiply with the most won- 

 derful rapidity. Thus it is that our increased knowledge regarding 

 micro-organisms or bacteria as the cause of many animal diseases has 

 emphasized the importance of disinfection. 



