42 SCIENCE FROM AN EASY CHAIR 



prevent the formation of these poisons that he has intro- 

 duced the use of sour milk, prepared with the lactic 

 ferment. Since the Cambridge celebration he has been 

 in London in order to examine the condition of certain 

 patients from whom a distinguished English surgeon has 

 found it necessary to remove the " large intestine." 

 Metchnikoff wishes to ascertain what bacteria, poison- 

 producing or other, are present in these patients, and what 

 is their general chemical condition now that this poison- 

 producing part of the digestive canal has been taken from 

 them. 



In Paris, Metchnikoff has some very interesting experi- 

 ments in progress with bats. He uses the large tropical 

 fruit-eating bats, or " flying foxes." They have a very 

 short intestine, and very few bacteria and of very few 

 kinds are to be found in its contents. On the other hand, 

 there are as many as thirty distinct kinds of bacteria 

 producing putrefaction or other chemical change in the 

 digestive canal of man and their quantity is gigantic. 

 They pervade the whole contents of the human digestive 

 canal by millions. By properly feeding the flying foxes 

 in his laboratory in Paris Metchnikoff has actually suc- 

 ceeded in getting rid of all bacteria from their digestive 

 canal, so that he now has adult mammalian animals, not 

 very remote from man in their structure, food, and internal 

 chemistry, which are absolutely free from the intestinal 

 parasitic bacteria which he supposes to cause poisoning 

 and senile changes in man. It is obvious, without 

 pursuing the matter into further detail here, that Metchni- 

 koff is now in a position to test his views as to the action 

 of particular kinds of bacteria he has animals which are 

 free from them. He can make an experiment, keeping 

 some of his bats still free from bacteria and causing some 

 to be largely infected by this or that kind, and he can 

 compare the result in regard to the health and chemical 



