28 MICROBES AND TOXINS 



problems of nutrition which affect most of all the general 

 health, the individual development, and the evolution of man. 

 That is why we pay special attention here to the intestinal 

 microbes as being the most important of all those which 

 inhabit the bodies of man and animals. 



The first problem in this question is the possibility of life 

 without microbes. 



Life without Microbes. — Life in general, as *e know 

 it on the surface of this earth of ours, is impossible without 

 the action of the micro-organisms. As some philosophers 

 have well said, "life is but a little mould growing on the 

 surface of a rather moist planet." But is it possible for certain 

 individuals to live free from bacteria, although of course 

 depending on the conditions produced by bacteria, and paying 

 tribute to bacteria by reason of the fermentations to which 

 they owe their origin and nourishment and by which one day 

 they are doomed to be dissolved ? 



Plants have bacteria both around their roots and in their 

 tissues. Animals have thousands of millions in their digestive 

 tubes. The microbial world not only surrounds them but 

 is in them. In our intestine there proceed fermentations 

 from which we can absorb the products. Is this to our 

 advantage or is it not ? 



It seems that plants derive only benefit. The bacteria prepare 

 for them their food. A sterile seed made to sprout in a sterile 

 nutritive fluid, such as milk, can use neither casein nor sugar 

 nor starch ; it secretes neither rennin nor casease, nor sucrase, 

 nor amylase. There is amylase, it is true, in the cotyledons of 

 the germinating seed, but its action does not extend into the 

 surrounding medium. Plants thus prosper by the help of 

 bacteria, and the aim of cultivators is to provide for each plant 

 the microbes most favourable for the yield desired by mankind. 

 But it is to be noted that these useful microbes are not within 

 the plant. 



The problem is quite otherwise in the case of animals. As 

 in so many other cases, the question was first stated by Pasteur 

 in connection with Duclaux's experiments on the nourishment 



