144 THE MORE CHRONIC INFECTIOUS DISEASES 



found by staining. Some of the material is then 

 introduced under the skin or into the peritoneal 

 cavity of guinea-pigs. If tubercle bacilli be present, 

 evidences of the disease will appear in these animals 

 in from two to five weeks. The bacilli can be found by 

 staining smears from the tubercles. Agglutinins are 

 formed in tuberculosis, but the clumping test is of 

 little value. 



The tuberculin reaction is a very important diag- 

 nostic measure. During its growth on artificial media 

 in the laboratory, the tubercle bacillus develops its 

 endo- and extra-cellular toxins. If these poisons, 

 called "tuberculin," obtained by removing the living 

 organisms from a fluid culture, be injected under or 

 rubbed into the skin, a characteristic reaction occurs. 

 The subcutaneous injection of as small a quantity as 

 5 milligrams or about yV minim of Koch's tuberculin 

 will cause a definite rise of temperature and a feeling 

 of general malaise within twenty-four hours. The 

 inunction of a drop of this solution into the skin, com- 

 bined with a slight irritation of the surface, will cause 

 a reddened papule or even a vesicle upon a swollen 

 base to appear within twenty-four hours. There are 

 several modifications of this skin test in practice, but 

 the principle is the same in all. It is claimed by many 

 that all adults have some tuberculosis in their body, 

 acquired during childhood, but which has remained 

 quiet or has healed completely. For this reason the 

 skin test may be positive in adults who are really not 

 suffering from their slight latent infection, and it is 

 therefore not reliable. It should only be used in chil- 

 dren. The supposed cause of the tuberculin test either 



