CHOLERA 157 



is in harmony with the well-known fact that vegetable poisons are always 

 stronger in the tropics than in temperate climates — the hashish of hemp, for 

 example. 



We see from the above facts that cholera is caused by a tropical aquatic 

 organism, a metatrophic bacterium, which is- not able to obtain a permanent 

 footing in our climate, but is introduced afresh from time to time through 

 the various channels of trade and communication. 



8. In addition to the well-known species of pathogenic bacteria already 

 described, there are many with which we are less familiar, the spirochaete 

 of relapsing fever, the glanders bacillus, swine erysipelas, and other animal 

 infections. In many diseases, such as rabies, scarlet fever, measles, 

 whooping-cough, the specific organisms, although supposed to be bacteria, 

 are not yet known. A few other pathogenic micro-organisms and fungi 

 were mentioned in Chapter IV. 



