458 Veterinary Medicine. 



But it fails entirely in cases in which the milk of unquestionably 

 tuberculous animals is free from bacilli, or in which the local 

 nodule or discharge tested is itself free from tubercle. It is a 

 test of the local lesion and not of the entire animal system. 



In choosing a subject for inoculation, the first consideration is 

 that it must come from a healthy stock and be itself free from 

 tuberculosis. Next, it must be of a species actively susceptible 

 to the habitual tuberculosis of the animal from which the inocu- 

 lated matter is taken. Thus for man, ox, dog and parrot, the 

 Guinea pig is especially appropriate, while for gallinaceae and 

 horses, the rabbit is to be preferred. Inoculation is usually made 

 into the peritoneal cavity. 



As a period of two or three weeks is usually necessary to 

 allow of an extensive development of tuberculosis, the method 

 must be too often discarded on account of the delay in obtaining 

 results. 



Tuberculin test. Many stock owners still entertain an ignorant 

 and unwarranted dread of the tuberculin test. It is quite true 

 that, when recklessly used by ignorant or careless people it may 

 be made a root of evil, yet as employed by the intelligent and 

 careful expert it is not only perfectly safe, but it is the only 

 known means of ascertaining approximately the actual number 

 affected in a given herd. In most infected herds, living under 

 what are in other respects, good hygienic conditions, 73 or ^ are 

 not to be detected without its aid, so that in clearing a herd from 

 tuberculosis and placing both herd and products above suspicion 

 the test becomes essential. 



Tuberculin is the bouillon in which the tubercle bacillus has 

 been grown, charged with the toxic products of its growth, but 

 which has been raised to a boiling temperature to destroy all 

 germ life, and from which the dead germs have been removed by 

 passing it through a porcelain filter. When a physiological dose 

 of this has been injected, subcutem, into the suspected animal, 

 it has 110 effect on the non-tuberculous, while in the tuberculous 

 it produces, in the course of the next 24 hours (usually from the 

 8th to the 1 6th), a steady rise of temperature by 2 F. or more, 

 followed by a slow subsidence to the normal. This may last for 

 from three to ten hours in different cases. 



Among the precautions may be named : 



