BOVINE TUBERCULOSIS 



Bovine tuberculosis is one of the oldest diseases of animals of which 

 we have knowledge. It was known to the Israelites in the days of their 

 captivity and from then until now it has been a subject of much thought 

 and investigation. The opinions that have been entertained concerning 

 it have been vacillating, the decrees of one century as to its supposed 

 infectious nature and the use of the flesh of the infected animals often 

 being reversed by those of the following century. History shows that up 

 to the time of the introduction of modern scientific methods for the study 

 of disease, there was little that was definite in our knowledge of tubercu- 

 losis beyond the fact that it was a very destructive disease of both men 

 and cattle. 



In 1865, tuberculosis was demonstrated to be infectious. In that 

 year, \'illemin showed that it could be produced in healthy animals by 

 inoculating them with pieces of tuberculous tissue. His results were con- 

 firmed by a number of other investigators. In 1882, Robert Koch dis- 

 covered the bacillus* (or micro-organism) of tuberculosis and thus com- 

 pleted the already abundant evidence that tuberculosis is a specific, 

 infectious disease. The finding of its specific cause led to many careful 

 and extended investigations into the nature of tuberculosis, the means by 

 which it is spread, and the measures that must be adopted if its spread is 

 to be checked. The results of these numerous inquiries have given us 

 very definite knowledge of the nature of the disease. It is believed that 

 this knowledge, if properly used, will enable every cattle owner to elimi- 

 nate tuberculosis from his herd, if it is there, and to keep it out, if it is 

 not there. 



In order to have a clear understanding of what kind of a disease tuber- 

 culosis is, it may be well to compare it with some disease that is generally 

 known and recognized to be infectious. For this we may take diphtheria 

 in children. It is well known that diphtheria is caused by a micro-organ- 

 ism. This organism is known as Bacillus diplithcricc, or sometimes as the 

 Klebs-Lceffler bacillus, from its discoverers. It is also known that when a 

 healthy child is exposed (infected) by being brought in contact with a 

 child sick with diphtheria, the period of incubation (that is, the time 

 elapsing between the exposure and the time the symptoms of the disease 

 appear) is but a few days, and that the duration of the disease is short, 

 lasting but a few days or weeks at the longest. At the end of this short 

 period, the entire course of the disease has been run and the child is either 

 dead or well on the way to recovery. 



^Bacteria (singular bacterium) is a general name for "germs" of a vegetable 

 or plant nature. A bacillus (plural bacilli) is one kind of bacteria, distinguished 

 by being much longer than broad. A micrococcus is a spherical bacterium. Gen- 

 eral terms used to designate many of these minute forms of life are " microbe," 

 " germ," or " micro-organism." 



Note. — This bulletin is a reprint of Bulletin 225, issued early in 1905, with 

 such changes and additions as are suggested by the increase of knowledge on 

 the subject. 



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