120 IMMUNITY. 



nervous substance must come into direct contact with the 

 toxin in order to be effective ; further, that it excited an 

 inflammatory reaction at the site of injection, and that this 

 alone was responsible for the resulting immunity. The brain 

 substance must be crushed, otherwise it is ineffective. Marie 

 found that the gray matter of the cerebral cortex possessed 

 the greatest immunizing power. Immunization by tissue- 

 suspensions has been practised for some time against tetanus 

 infection, but the results have not been very satisfactory. 

 Extracts of the liver and the adrenals have been found to 

 counteract the cobra poison. 



Inert substances : By mixing commercial carmine with 

 tetanus toxin in the proportion of 0.5 gram to 10 c.c., the 

 toxicity of the toxin is reduced considerably. By heating 

 this mixture to 60 C., its protective action is destroyed; but 

 twenty-four hours afterward the mixture has regained its 

 toxicity, so that the toxin is not destroyed by the carmine. 

 This peculiar action of the carmine is probably the result of 

 the leucocytosis produced by the inflammatory reaction of 

 the tissues when the mixture is injected. 



MODIFICATION OF IMMUNITY : Inasmuch as immunity is 

 at all times only a relative and not an absolute condition, we 

 will now consider briefly those conditions which modify 

 immunity. Exaltation of immunity is synonymous with 

 acquired immunity, which we have gone into already. The 

 modifications that are of vital importance are those which 

 tend to lessen the immunity. They are all manifested by a 

 diminution of the resistance of the tissues to infection. 



Exposure to cold: This is one of the most potent agents in 

 the reduction of immunity. Many infectious diseases follow 

 " taking cold," especially pneumonia, tuberculosis, and other 

 affections of the respiratory system. 



Fatigue has a decided tendency to reduce tissue resistance, 

 and consequently the immunity. 



Poor hygiene : It is a matter of every-day observation that 

 epidemics of infectious diseases are much more common under 

 poor hygienic conditions than where these do not prevail. 

 Living in small, stuffy rooms to which sunlight and fresh air 

 have little or no access, overwork, insufficient sleep, worry, 



