78 PATHOGENIC BACTERIA. 



On the other hand, Schottelins ! hatched and kept some 

 chickens under conditions of absolute sterility. The birds 

 did fairly well in the beginning, but gradually pined and 

 died on the seventeenth day. The control-chickens, 

 whose digestive organs contained bacteria, thrived. 



e. The Sexual Apparatus. — The vagina has a flora of 

 its own, consisting of a limited number of species that 

 are able to endure its acid secretions. 



The uterus seems to be well guarded from bacterial in- 

 vasion by the acid secretions of the vagina and by the 

 alkaline cervical mucus. According to the studies of 

 Gottschalk and Immerwahr, 2 twenty-one out of sixty 

 cases of endometritis which they studied bacteriologic- 

 ally were characterized by sterile discharges. 



The penis and the vulva, in addition to the micro- 

 organisms of the skin, contain in the smegma a peculiar 

 bacillus — Bacillus smegmatis (q. v.) — which, while not 

 known to be a pathogenic bacterium, is easily mistaken 

 for the bacillus of tuberculosis. 



f. The external ear, being a canal of some depth, can- 

 not fail to collect bacteria, and furnishes a certain non- 

 pathogenic coccus, the Micrococcus cereus flavus, with 

 great regularity. Whatever micro-organisms happen to 

 enter may be found near the external meatus, but toward 

 the tympanic membrane there are very few. 



With so large and varied a permanent flora upon and 

 in our bodies we need not look far for the sources of the 

 common infections. We carry them constantly with us, 

 and are ever in danger from them. _ Fortunately it seems 

 that something more than a breach in the continuity is 

 necessary to enable them to harm us. Injuries of all 

 parts of the body are common, but consequent infection 

 is uncommon. For infection to occur it is necessary that 

 bacteria (i) enter the tissues, (2) in a sufficient number, 

 (3) when the usual resisting power is diminished. The 

 element of numbers is an important one to consider in 



1 Miinchener med. Wochenschrift, 1898, No. 36. 



2 Archivf. Gynak., 1896, Bd. 50, H. 3. 



