CHAPTER II. 

 BIOLOGY OF BACTERIA. 



THE distribution of bacteria is wellnigh universal. 

 They and their spores float in the atmosphere we breathe, 

 swim in the water we drink, grow upon the food we eat, 

 and luxuriate in the soil beneath our feet. Nor is this 

 all, for, entering the palpebral fissures, they develop upon 

 the conjunctiva ; entering the nares, they establish them- 

 selves in the nose ; the mouth is always replete with 

 them ; and, as many are swallowed, the digestive appa- 

 ratus always contains them. The surface of the body 

 never escapes their establishment, and so deeply are 

 some individuals situated beneath the epithelial cells 

 that the most careful washing and scrubbing and the use 

 of the most powerful germicides are required to rid the 

 surgeon's hands of what may prove to be dangerous 

 hindrances to the healing of wounds. The ear is not 

 without its microscopic flora ; special varieties live be- 

 neath the finger-nails, and especially the toe-nails, in 

 the vagina, and beneath the prepuce. 



While so general, however, they are not ubiquitous. 

 Tyndall succeeded in proving that the atmosphere of 

 high Alpine altitudes was free from them, and likewise 

 that the glacier ice contained none. Wherever man, ani- 

 mals, or even plants, live, die, and decompose, bacteria 

 are sure to be present. 



Notwithstanding their extreme familiarity with the 

 animal body, there are certain parts of it into which 

 bacteria do not enter, or, entering, remain vital for a 

 very short time, for the body-juices and tissiies of normal 

 animals are free from them, and their occurrence there 

 may almost always be accepted as a sign of disease. 



The presence of bacteria in the air is generally de- 



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