BACTERIA IN NATURE 11 



of the sweat glands. In like manner the mucous mem- 

 brane of the intestine harbors certain species of bacteria. In 

 a soil that is richly fertilized with organic matter a still 

 greater variety of bacteria is found. The difference in the 

 species that are found in these different substances and 

 places is so pronounced that they are spoken of with con- 

 siderable denniteness as the bacterial flora of these particu- 

 lar substances or places such for example as the bacterial 

 flora of spring water, of milk, of the skin, and of the intes- 

 tine. It must be understood that other bacteria are fre- 

 quently present and that all the species of these different 

 flora are never present in any individual case. 



When reference is made to a bacterial flora it is import- 

 ant to distinguish between the organisms which become 

 localized and multiply in a given place and which consti- 

 tute its flora and the bacteria which are brought to the place 

 by accident. Thus, in the intestine, the bacteria of the con- 

 tents brought there with the food must be distinguished 

 from those that inhabit the mucous membrane and which 

 appear in cultures made from the scrapings of the mucosa 

 after the contents have been washed off with sterile water.* 



* For a study of the bacteria of the digestive tract the student 

 is referred to the work by Herter (Bacterial infections of the di- 

 gestive tract, MacMillan Co., 1907). Bullard (Am. Med. Vol. IV 

 (1902) p. 546.) showed that the B. coli invasion of the intestine of 

 rabbits depended largely upon their environment. Lober (Am. Med. 

 Vol. VII (1904) p. 152) found that the intestinal flora of fish from 

 Cayuga Lake did not contain B. coli but B. proteus were quite com- 

 mon. Ward (Bulletin 178, Cornell Agric. Exp. Station, 1900) found' 

 certain species of bacteria throughout the udder. In the 19 speci- 

 mens examined there was great uniformity in the species revealed. 

 Bacteria not commonly present in the udder may occasionally gain- 

 entrance and remain for a shorter or longer time. King (Amer. 

 Med. Vol. X (1905) p. 400) found the bacterial flora of the intestinal 

 mucosa of the fowl to be quite constant and to consist of about 50> 

 species. He found the flora in the different fowls to vary somewhat 

 according to the conditions under which they had been kept. He 

 also studied the flora of the conjunctiva and found that it consisted" 

 of a few species distributed between the genera bacterium and micro- 

 coccus. 



