l80 BACTERIA 



has recently been engaged in isolating from poisoned foods 

 the different species of bacteria present. It would appear 

 that these are limited, as a rule, to two or three kinds. As 

 regards disease, the organisms of suppuration are the most 

 common. Liquefying or fermentative bacteria are fre- 

 quently present, the Proteus family being well represented. 

 In addition there are, according to circumstances, a number 

 of common saprophytes. Now, as we have pointed out, 

 these organisms may act injuriously by some kind of co- 

 operation, or they may by themselves be harmless, and 

 pathological conditions be due to the occasional introduc- 

 tion of pathogenic species. 



The other fact, requiring recognition from anyone who 

 proposes to study the bacteriology of foods, is that a certain 

 appreciable amount of the responsibility for food poisoning 

 rests with the tissues of the individual ingesting the food. 

 There is ample evidence in support of the fact that not all 

 the persons partaking of infected food suffer equally, and 

 occasionally some escape altogether. We know little or 

 nothing of the causes of such modification in the effect 

 produced. It may be due to other organisms, or chemical 

 substances already in the alimentary canal of the individual, 

 or it may be due to some insusceptibility or resistance of 

 the tissues. Be that as it may, it is a matter which must 

 not be neglected in estimating the effects of food contamin- 

 ated with bacteria or their products. 



Milk, There are few liquids in general use which contain 

 such enormous numbers of germs as milk. To begin with, 

 milk is in every physical way admirably adapted to be a 

 favourable medium for bacteria. It is constituted of all the 

 chief elements of the food upon which bacteria live. It is 

 frequently at a temperature favourable to their growth. It 

 is par excellence an absorptive fluid. A dish of ordinary 

 water and a dish of newly drawn milk laid side by side, and 

 under similar conditions of temperature, will rapidly demon- 



