172 MANUAL OF BACTERIOLOGY. 



CHAPTER VI. 



TOXINS. 1 



IT is now generally believed that in most, if not all of 

 the infectious diseases, the principal symptoms and lesions 

 are to be attributed to the action of poisonous substances 

 formed by the bacteria. The part that bacteria play can 

 be understood best by recalling the work of the saprophytes 

 in producing fermentation and putrefaction. It has already 

 been shown that the poisoning that comes from eating de- 

 composed meat, fish, or cheese results from poisons which 

 bacteria have elaborated in the course of their growth. 

 In infectious diseases we suppose the bacteria to grow in- 

 side of the body and to form their poisons in it; not before 

 their introduction into it, as in these cases of poisoning with 

 spoiled food. If it were possible for the cells of ordinary 

 yeast to grow in the living human body and to produce 

 alcohol from the grape-sugar of the body-fluids, the person 

 so infected might be expected to suffer from alcoholic in- 

 toxication as long as the infection lasted. This impossible 

 illustration although not entirely accurate may help to make 

 clear what does happen in an infectious disease due to bac- 

 teria, where poisons formed in a manner analogous to the for- 

 mation of alcohol produce intoxications analogous to alco- 

 holic intoxication. Certain infectious diseases exhibit the 

 element of poisoning by bacterial products in an extremely 

 marked manner. In tetanus the local wound may be trifling, 

 and may seem utterly incapable of having given rise to the 



1 For a full consideration of this subject see Vaughan and Novy, 

 " The Cellular Toxins," 1902. 



