NATURAL RESISTANCE AND FATIGUE 147 



in part, by the injection of non-specific (i.e., heterolo- 

 gous) proteins which, so far as is known, bear no re- 

 lation whatsoever to the bacterial products (see re- 

 view by Petersen, 1928). 



For example, numerous clinical investigators have 

 reported that they have obtained encouraging results 

 in the treatment of arthritis by the intravenous injec- 

 tion of divers substances, such as dead typhoid bacilli, 

 or sterile milk. Such substances obviously bear no re- 

 lationship to the causative factor in arthritis; yet in 

 some mysterious way they are able to stimulate the 

 animal's resistance towards the primary factor respon- 

 sible for the pathological condition. The very nature 

 of the treatment indicates that this increase in resist- 

 ance is brought about in a non-specific fashion: that 

 is, in some manner other than by the elaboration of 

 antibodies specific for the invading organism causative 

 of arthritis. 



With these facts before us, it is of interest to exam- 

 ine their possible relationship to some observations of 

 the writer concerning the nature of natural resistance. 



Many years ago, in connection with the experiments 

 previously mentioned wherein emulsions of mustard 

 were introduced into the stomachs of dogs, at fre- 

 quent intervals for a period of some months, the ani- 

 mals gradually developed a tolerance for the markedly 

 irritating substance. This was evidenced by the fact 

 that after several weeks of such treatment the animals 

 failed to expel the stomach contents following the in- 

 troduction of the mustard. While this observed fact 

 may appear quite remarkable, it is of interest to note 

 that it is analogous to the distinct tolerance which cer- 

 tain Oriental and tropical peoples have developed to- 



