PRACTICAL APPLICATIONS 387 



tuberculous should be removed from the infection and placed 

 under good hygienic conditions. A few injections of TR may be 

 given, however, and analogy with a similar procedure in cattle 

 would lead us to believe that it may be of some value. 



Attempts to immunize lower animals to tubercle have been 

 made from a very early period ; it was, indeed, the discovery of 

 the fact that dead bacilli are absorbed with great difficulty that 

 led Koch to devise his TR. The vaccines that have been employed 

 are numerous cultures of low virulence, dead cultures, avian 

 and reptilian bacilli, etc. but the subject entered on a new and 

 most important phase in 1901, when von Behring published his 

 method, which is of great theoretical interest, and from which 

 important practical results in the stamping out of bovine tubercle 

 (so great a pest to infants, from the prevalence of bacilli in milk) 

 have been esteemed possible. Here the vaccine consists of living 

 tubercle bacilli of human origin. This is of feeble virulence for 

 cattle. It is prepared by being dried in vacuo, emulsified with 

 glycerin in a mortar, and diluted with normal saline solution 

 containing 0*15 per cent, of sodium carbonate. It is standardized 

 in such a way that i c.c. = 2 milligrammes of dried bacilli. The 

 injections are made intravenously; two are given the first of 

 i c.c., and the second, about twelve weeks later, of five times this 

 amount. 



There is no doubt that this process confers a certain amount 

 of immunity, or rather of increased resistance. The process is 

 harmless to calves, but sometimes kills older animals from 

 pulmonary redema. The immunity lasts for a year or so. 



The method has been carefully examined at Melun by Rossignol 

 and Vallee, and their results were quite favourable. The 

 vaccinated animals were tested (along with controls) by sub- 

 cutaneous injection of bovine tubercle, by injections of these 

 bacilli into the veins, and by keeping them in a shed with animals 

 known to be tuberculous, and in all cases a greatly increased 

 degree of resistance was found. But Lignieres pointed out a 

 remarkable fact, that animals which have been treated in this 

 way and which do not react to tuberculin, and are apparently 

 normal at the autopsy, nevertheless may contain living tubercle 

 bacilli in their lymphatic glands. This is of extreme interest in 

 connection with the question of the latency of bacilli in the tissues. 



Von Behring's latest vaccine is known as tuberculase, or tulase. 

 It appears to be prepared by the action of chloral on tubercle 



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