THE BACTERIA OF THE NORMAL HUMAN BODY. 165 



aerogenes. More recently it has been shown that the stools 

 of milk-fed infants, and to a less extent of adults, contain large 

 numbers of anaerobic bacilli, which stain by Gram's method 

 (bacillus bifidus — Tissier, bacillus acidophilus — Moro) . These 

 bacteria have not been fully studied*. 



The number of bacteria in a milligram of human fecal 

 matter has been estimated at from seventy thousand to thirty- 

 three million.f It is estimated that about one-third of the 

 fecal matter of adults if dried would be found to consist of 

 bacteria. J The small intestine of adults has been found by 

 different observers to contain very different species. § The 

 majority of these appear to have been introduced from the 

 mouth in food or water. The bacillus coli communis, however, 

 occurs invariably in health not only in the intestine of man, but 

 also in that of many animals, especially in the lower part. || 

 The pyogenic micrococci very often occur in the intestine. 



In the case of ruminant animals like the cow and sheep, 

 the decomposition of cellulose, which forms so large a part of 

 their food, appears to be affected by bacteria. Bacteria having 

 this power are constantly found in the stomachs of ruminants. 

 The best known species is that called bacillus amylobacter. It 

 is questionable whether the products of the decomposition of 

 cellulose have any nutritive value. 



Pasteur some years ago expressed the opinion that if animals could be placed 

 in such surroundings that bacteria could be excluded from the alimentary canal 

 and the food, life would be impossible. This view has excited much controversy, 

 and was apparently disproved by the experiments of Nuttall and Thierfelder. 



*Metchnikoff. Les Microbes Intestinaux. Bulletin de I'Institut Pasteur. 

 May 15 and 30, 1903. 



t Our method for estimating the number of bacteria in feces see Steele. 

 Journ. Am. Med. Assn., XLIX., Aug. 24, 1907, p. 647. 



X Strassburger Centrallbel. f. Bakt., etc. Ref. Bd. 32. p. 561. 



JFord. Classification of Intestinal Bacteria, etc. Studies from the Royal 

 Victoria, Montreal. March, 1903. 



||Moore and Wright. Bacillus coU communis from Certain Species of Domes- 

 ticated Animals. American Medicine. March, 1902. 



