140 Bulletin 65. 



culin" on the animal system? It produces a constitutional dis- 

 order with elevation of the body temperature, commonly known 

 as fever, and an impairment of most of the bodily functions, nota- 

 bly those of assimilation and secretion. This is abundantly man- 

 ifest in the wasting and fever of the victim of acute tuberculosis 

 in which these poisonous principles are being constantly produced 

 in large quantities. As the dose is reduced, a point is finally 

 reached at which no fever nor appreciable systematic derangement 

 is produced, and thus in many slight and indolent cases of tuber- 

 culosis the animal appears well, and thus, also, the usual test 

 dose of tuberculin has no recognizable disturbing effect on the 

 healthy animal system. With a dose less than this it may even 

 be questioned whether it maj'- not be actually beneficial in con- 

 ferring on the healthy system a small measure of tolerance and 

 power of resistance to the bacillus and its poisons. This, how- 

 ever, is of little account, seeing that no real immunity from tuber- 

 culosis is ever acquired. In many systems, both human and 

 brute, the disease continues its slow progress for many years, and 

 the slight tolerance that results, while it may suppress the dis- 

 ease so that it assumes an indolent and chronic form, does not 

 fully arrest it. 



Very different is the effect of even a minimum dose of tubercu- 

 lin on a subject which is already attacked with tuberculosis. In 

 such a case the products of the existing tubercle, circulating in 

 the blood and tissues, are often so small in amount and the sys- 

 tem has acquired such a tolerance of them that there is no mani- 

 fest disturbance of health and the animal ma}- even be in excellent 

 condition. But add to this minimum amount of poison already 

 in the sj^stem a small quantity of tuberculin and in ten or fifteen 

 hours the temperature of the patient's body will rise two or more 

 degrees above the normal, and the destructive process going on 

 in the seats of the tubercles will be accelerated. In cattle this is 

 now used as a most valuable test of the presence or absence of 

 occult tubercle. In horses and other animals, the subjects of 

 of tuberculosis, ' ' tuberculin ' ' causes the same rise of temperature, 

 and this rise may be accepted as a rule applicable to all classes of 

 animals. In the tuberculous man this action of " tuberculin " is 

 a well established fact, and was made the basis of Koch's employ- 



