MICROBES IN THE HUMAN BODY 41 



But here we were still only dealing with growth on plates, 

 i.e., under very artificial conditions. The importance of the ex- 

 periments increased when it was found possible to transmit to 

 an animal, with certainty, a genuine attack of cholera. Neither 

 the cat nor the guinea-pig nor the adult rabbit takes the 

 disease. Metchnikoff had the idea that their resistance might 

 be due to the presence in the alimentary canal of inhibiting 

 bacteria, and he experimented accordingly on little sucking 

 rabbits, which, while they are at the breast a period of some 

 weeks present a very scanty intestinal flora. Little rabbits of 

 one to four days old, made to swallow a culture of the cholera 

 vibrio, died in about half the cases ; they were thus capable of 

 taking cholera. But further, when to the culture of the vibrio 

 other bacteria were added which had been recognised as 

 being favouring in the gelatine experiment, the little rabbits 

 took cholera without exception. They were refractory, on the 

 contrary, when the inhibiting bacteria were added. 



The question naturally arose whether during an epidemic 

 man might not increase his resistance to a cholera infection 

 by ingesting cultures of these inhibiting microbes, and this 

 formed the starting point of intestinal bacteriotherapy. 



Bienstock attributed the resistance which milk possesses 

 naturally towards putrefaction to the microbes which it contains, 

 and not, as the old idea maintained, to the presence in it of 

 casein or milk sugar ; he found that the B. lactis aerogenes, an 

 acid producer, and even the B. coli, prevent the development 

 of the B. putrificus, the agent of putrefaction, whether in an 

 experimental flask or in the intestine. Inoculated along with 

 the B. coli, the growth of B. putrificus is inhibited, because it 

 can only develop in an alkaline medium, and the B. coli 

 produces from the sugars of the food materials an abundance 

 of acid. 



The idea of an inhibiting action exerted by an acid-producing 

 bacterium on the putrefying organisms is correct, but the above 

 example was not the best ; in the first place because the 

 B. putrificus is rare in the human intestine, and secondly 

 because the B. coli, while playing a useful part in certain cases, 



