THE MICKOBES OF HUMAN DISEASES. 239 



poisonous substances greatly resembling vegetable 

 alkaloids, and termed by them ptomaines. 



The action of ptomaines may be compared to that 

 of strychnine. Injected into the blood, even after 

 the removal of every living microbe, the ptomaines 

 produce fever, rigors, vomiting, diarrhoea, spasms, 

 torpor, collapse, and finally death. It is probable that 

 in some cases of poisoning by tainted meat or fish 

 their poisonous properties are due to the presence of 

 ptomaines. 



But in all cases these ptomaines are shown to be 

 the product of putrid fermentation, which is always 

 effected in dead bodies by special microbes. Here the 

 ptomaines are due to the work of the microbes of 

 putrefaction, and are made by them, just as alcohol 

 and the carbonic acid of alcoholic fermentation are 

 made by yeast, at the expense of the sugared liquid 

 in which they live and multiply. 



Direct experiments show that when septine, from 

 which every microbe has been removed, is injected 

 into the human subject, it produces feverish disturb- 

 ance, but only causes death when introduced in con- 

 siderable quantities. If, on the other hand, there is 

 in the same individual a large suppurating wound, 

 exposed to the air instead of being covered by an air- 

 tight dressing, a purulent infection (septicaemia) will 

 almost certainly ensue, since the microbes introduced 

 by means of this wound will find in it a favourable 

 soil (pus and putrefying organic matter); they will 



