BACTERIAL INVASION 223 



tion, it is obvious that those individuals having the 

 greatest resistance towards cytost will be the best 

 equipped to offset the ravages of the microorganisms. 

 Consequently, the employment of any of the methods 

 discussed in the chapter on natural resistance, which 

 may raise an individual's resistance to cytost, may be 

 expected to result in an increased resistance towards 

 bacterial invasion. 



It must be noted that such an increased resistance 

 is non-specific, and would not offer an immunity 

 towards specific toxins, such as diphtheria toxin. 

 Nevertheless, that cytost may play a role in the devel- 

 opment of specific immunity is indicated by some re- 

 cent experiments of Bresredka (1931), who found 

 that the application of friction to the shaved skin of 

 a rabbit was sufficient to endow the animal with a local 

 non-specific immunity towards bacterial toxins, which 

 lasted for from twelve to fourteen hours. If during 

 this period an ointment^ containing diphtheria toxin 

 is applied to the skin, the animals are found to develop 

 a specific immunity to the toxin. This is at first purely 

 local, and later becomes general. 



In a previous chapter we have called attention to 

 the experiments of Lewis and his associates, which 

 demonstrated that prolonged gentle friction on the 

 unbroken skin leads to a localized reaction identical 

 with that which follows the intradermal injection of 

 tissue extracts. As previously stated, this indicates 

 that such gentle friction is sufficient to cause the liber- 

 ation of cytost. 



Such being the case, it seems clear that the immune 

 reactions observed by Bresredka were due to the re- 

 lease of cytost, which was brought about by the rub- 



