MICROBES IN THE HUMAN BODY 27 



not only the common bacteria, the streptococci and staphylo- 

 cocci, but also pathogenic bacteria, which take shelter there 

 and remain latent until an opportunity offers to multiply ; 

 examples are the diphtheria bacillus, the microbe of pneumonia, 

 and that of cerebro-spinal meningitis. 



In the deeper respiratory passages, there are few microbes ; 

 there they may be numbered by units. But it is proved that 

 the tubercle bacillus can penetrate with the inspired air right 

 to the bottom of the pulmonary alveoli. 



The mouth, the vestibule of the digestive tube, contains 

 already a large proportion of the microbial species which 

 populate the stomach and intestine, e.g., staphylococci and 

 streptococci, resembling those of the skin, bacilli, aerobic 

 and anaerobic, resembling those found both in the healthy 

 intestine and in the intestine and appendix in disease, and finally 

 a whole flora peculiar to the mouth which plays a part in dental 

 caries. 



The stomach being acid suits moulds and yeasts better than 

 bacteria. However, about thirty species of bacteria have been 

 described in it (Coyon), several of which have attracted special 

 attention because of the idea that they might favour or inhibit 

 the penetration of certain pathogenic bacteria into the intestine. 

 ' All the cavities and recesses of the human body deserve 

 study from the point of view of their flora. Many species have 

 been seen but are not yet well known, because we do not yet 

 know how to cultivate them artificially. 



The flora hitherto most studied is that of the intestine. It 

 is also the most important. The intestine is the great laboratory 

 of digestion, and at the same time, unfortunately, of putrefac- 

 tions, the products of which are absorbed by the body. 

 Hence one may say that man, like other animals, is dependent 

 on his belly, and no system of therapy is justified in neglect- 

 ing it. Just as the soil outside of us is, in nature, the great 

 microbial reservoir, so in us the great reservoir of microbes is 

 our intestine. 



Under the impulse of Metchnikoff, the intestine has with 

 justice become the great field of study and experiment in those 



