84 BACTERIAL POISONS OF INFECTIOUS DISEASES. 



culin the dead bacilli were often carried from the place of deposit and 

 distributed by means of the circulation to different parts of the body 

 where subsequently tubercular nodules formed. 



The physiological action of tuberculin is so pronounced and at first 

 was believed to be so markedly sui generis, that its discoverer, and 

 through him the greater part of the medical world, was for a short 

 time led into the belief that a specific and sure cure for the greatest 

 plague of man had been found. The grounds for this belief were 

 founded principally upon the following efiects observed in the action 

 of tuberculin : (1) Small doses, one mg. or even less, injected subcu- 

 taneously into individuals sufiering from tuberculosis caused marked 

 elevation of temperature ; while similar doses injected in the same way 

 into non-tubercular persons produced no appreciable effect. More- 

 over, persons sick with other diseases than tuberculosis were not 

 found to be especially susceptible to the action of tuberculin. Here, 

 then, is a substance that has a specific action, a chemical body by the 

 effects of which one can distinguish a tubercular from a non-tuber- 

 cular individual. If all the cows of a large herd be treated with 

 tuberculin in proper amount, and a record of the temperature be 

 made for twenty-four hours before and for the same length of time 

 after the treatment, it will be found that in some a febrile reaction — 

 an elevation of one degree or more in temperature — occurs, while the 

 temperature of others remains unaffected, or is but slightly changed. 

 Now, if all these animals be killed and examined, it will be found 

 that those that have manifested the febrile reaction are tuberculous ; 

 while those that failed to react to tuberculin are not tuberculous. 

 A similar test to this was made by Koch on tuberculous and non- 

 tuberculous guinea-pigs. No such effects had ever before been &t- 

 tained by the employment of any therapeutic agent. It is small 

 wonder then that Koch and his colaborers were surprised at the re- 

 sults observed, and readily accepted and too speedily announced the 

 belief that a specific cure for tuberculosis had been found. The 

 grounds for this belief were strengthened by their observation of 

 additional evidence in the selective action of tuberculin. 



(2) Not only does tuberculin select tubercular individuals by its 

 action, but in the individual it selects for the demonstration of its most 

 conspicuous effects, the exact site of the tubercular lesion. If a man 

 who has a lupus on his face receives a tuberculin injection in the 

 back or in any other portion of his anatomy, the tissue about the 

 lupus soon begins to show evidence of stimulation ; it becomes hy- 

 peremic, the margins of the sore begin to granulate, and if the 

 treatment be continued the lupus often temporarily heals. How- 

 ever, more extended investigation has shown that the action of 

 tuberculin is not so specific as was at first believed. The experi- 

 ments of Krehl have demonstrated the fact that tubercular animals 

 are especially prone to show elevations of temperature after the in- 



