BACTERIOLOGICAL EXAMINATION OF MATERIAL 211 



Examination of Feoes. Human feces contain an enormous num- 

 ber of bacteria of many varieties. Klein, 2 by special methods, 

 estimated that there were about 75,000,000 bacteria in one milligram 

 of feces. It has been a noticeable result of all the investigations 

 upon the feces, that although enormous numbers can be counted 

 in morphological specimens, only a disproportionately smaller num- 

 ber can be cultivated from the same specimen. This is explicable 

 upon the ground that special culture media are necessary for many 

 of the species found in intestinal contents and upon the consideration 

 that many of the bacteria which are present in the morphological 

 specimen are dead, showing that there are bactericidal processes 

 going on in some parts of the intestinal tract, possibly through the 

 agency of intestinal secretions, bile, and the action of the products 

 of metabolism of the hardier species present. By far the greater 

 part of the intestinal flora consists of members of the colon group, 

 bacilli of the lactis aerogenes group, Bacillus faecalis alkaligenes, 

 Bacillus mesentericus, and relatively smaller numbers of strepto- 

 cocci, staphylococci, and Gram-positive anaerobes. Many other 

 species, however, may be present without being necessarily con- 

 sidered of pathological significance. Certain writers have recently 

 laid much stress upon a preponderance of Gram-positive bacteria in 

 specimens of feces, claiming that such preponderance signifies some 

 form of intestinal disturbance. Herter 3 has recently advanced the 

 opinion that the presence of Bacillus aerogenes capsulatus in the 

 intestinal canal is definitely associated with pernicious anemia. This 

 is discussed in another section. The determination of these bacilli 

 in the stools is made both by morphological examination by means 

 of Gram stain and by isolation of the bacteria. Such isolation is 

 easily done by the method of Welch and Nuttal. 4 A suspension of 

 small quantities of the feces in salt solution is made and 1 c.c. of 

 the filtered suspension is injected into the ear vein of a rabbit. 

 After a few minutes the rabbit is killed and placed in the incubator. 

 After five hours of incubation, the rabbit is dissected, and if the 

 Welch bacillus has been present in the feces, small bubbles of gas 

 will have appeared in the liver from which the bacilli may be cul- 

 tivated in anaerobic stab cultures. 



-Klein, Ref. Cent. f. Bakt., I, xxx, 1901. 



3 Herter, < ' Common Bacterial Infections of the Digestive Tract, ' ' N. Y., 1907. 



* Welch and Nuttal, Bull. Johns Hopkins Hosp., 1892, 111, 81. 



