124 Bulletin 65. 



though these were abundant enough in the animal from which it 

 was taken, or the guineapig may have become infected after the 

 inoculation from being kept in an infected place, or from infected 

 food, water, attendants, etc. We must first secure for the guinea- 

 pig the very guarantee we are seeking for the larger animal. Is 

 it not then better to secure this for the larger animal first and 

 avoid all the subsequent sources of fallacy attendant on an inocu- 

 lation experiment ? 



The tuberculhi test gives prompt results and is less open to 

 fallacy. 



Ttiberculin. 



Tuberculin or Koch's lymph consists in the concentrated, 

 sterilized liquids in which the bacillus tuberculosis has been 

 grown. It contains no living bacillus ; all germs have been killed 

 by heating ; but it does contain the chief poisons which are pro- 

 duced in the tuberculous body, and which bring about all the 

 diseased processes in such body. A possible exception may be 

 made of any such poisons as are destroyed by heat if any such 

 there be, in tuberculous products. It must be distinctly under- 

 stood that in every contagious disease there is, ist, the germ 

 which grows and multiplies in the susceptible animal system, but 

 is not, in itself and by its mere presence, necessarily injurious, 

 and, 2d, the products of the life of that germ which may or may 

 not be poisonous. The many germs, which continually enter the 

 animal body, have products that are not appreciably poisonous 

 and therefore produce no disease, whereas the few that do manu- 

 facture poisonous products cause our diiferent contagious diseases. 

 We find a counterpart in the yeast germ which in itself is virtually 

 harmless to man, whilst the alcohol, which it manufactures from 

 sugar under certain conditions, is a poison more or less hurtful 

 according to the susceptibility of the person taking it. 



Tuberculin consists of chemical poisons which the bacillus 

 secretes or manufactures, and on which the force and all the mani- 

 festations of tubercle in the tissues are chargeable. Having no 

 living germ it cannot increase its own substance, nor can it cause 

 tuberculosis in a healthy system as it is soon thrown out of the 

 body through the kidneys and other channels and its power for 

 evil is at an end, yet none the less is it the immediate agent 



