EXAMINATION OF MATERIAL FROM PATIENTS 177 



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 mem- 

 bers of the colon group, bacilli of the lactis aerogenes group. Bacillus 

 fsecalis alkaligenes, Bacillus mesentericus, and relatively smaller num- 

 bers of streptococci, 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 speci- 

 mens of feces, claiming that such preponderance signifies some form 

 of intestinal disturbance. Herter ' has recently advanced the opinion 

 that the presence of BaciUus aerogenes capsulatus in the intestinal canal 

 is definitelj'^ associated with pernicious anemia. 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 isola- 

 tion is easily done by the method of Welch and Nuttal.^ 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 wiU have appeared in 

 the liver from which the bacilli may be cultivated in anaerobic stab- 

 cultures. 



Bacteriological examination of feces is most often undertaken for 

 the isolation of Bacillus typhosus. This is accomplished with a great 

 deal of difficulty because of the overwhelming numbers of colon bacilli 

 which easily outgrow the typhoid germs, and because of the similarity 

 of their colonies in most media. Many methods have been devised for 

 this purpose, all of which depend upon the use of special media aimed 

 at the inhibition of colon and other bacilli and the production of recog- 

 nizable differences in the colonies of typhoid and colon bacilli. Such 

 media are those of Eisner, Hiss, Conradi-Drigalski, LoefHer, Hesse, and 

 others, which are described in the section updn special media. (See page 

 133.) The methods of using these media will be found described in the 

 chapter on Bacillus typhosus (p. 399.) 



Cholera spirilla may be recognized in and isolated from the stools of 

 patients by morphological examination, and by cultivation. (See 

 section on Sp. cholerse.) 



> Herter, " Common Bacterial Infections of the Digestive Tract,'' N. Y., 1907. 

 2 Welch and Nuttal. See ref. p. 469. 

 13 



