648 BACTERIA OF THE INTESTINAL TRACT 



acidophilus of Mcintosh and others. The last-named organism is one which is ap- 

 parently identical with the "B. acidophilus''' of Bunting and his associates,' which was 

 recovered by different investigators from the cavities of decayed teeth and claimed 

 by them to be responsible for dental caries. Recent investigation has shown that L. 

 acidophilus as now recognized bears only certain minor resemblances to the organism 

 associated with caries, and that in many important respects the two are entirely dif- 

 ferent. 



METHODS OF FECAL EXAMINATION 



No serious attempts have been made as yet to establish standard bacteriological 

 methods of fecal examination, and there have been almost as many different proce- 

 dures as investigators. Different aims have led to the use of different methods. Only 

 a few of these will be given here. 



MacNeal, Latzer, and Kerr' were concerned with the following: the numbers and 

 quantity of bacteria, nitrogen determination, and differential count. After mixing with 

 a spatula or mortar and pestle, in order to obtain uniform test samples, i : 100 suspen- 

 sions in saline solution were prepared in 500-cc. glass-stoppered flasks, as a basis for 

 study. The total quantity of bacteria was determined by three different procedures: 

 the Eberle-Klein (plain slide) microscopic method; the method of Winterberg (Thoma- 

 Zeiss blood-counting chamber); and the gravimetric method of Strasburger (frac- 

 tional separation by washing and centrifuging, and weighing of dried bacterial residue). 

 The original methods were modified to suit the occasion more adequately. The ni- 

 trogen in the bacterial residues was determined by the Kjeldahl method. From the 

 nitrogen factors the average daily bacterial nitrogen in the feces and the percentage 

 of total fecal nitrogen represented were calculated. Differential bacterial counts were 

 made by a modified gram staining method in which the decolorizing was done with 

 anilin-xylol followed with methyl alcohol. 



Morris, Porter, and Meyer,^ in their investigation of the fecal flora of children, 

 had as their chief aim the establishment of a standard by which the activities of the 

 fecal flora of children could be recognized. This they hoped to do by the use of cer- 

 tain culture media and by microscopic examination. Stock suspensions of the feces 

 were prepared by emulsifying 500 mg. of feces with 50 cc, of saline solution in small 

 Erlenmeyer flasks. 



The following constituted a complete routine examination: (i) microscopic ex- 

 amination and differential counts of gram stained smears; (2) the use of the fermenta- 

 tion-tube method of Herter and Kendall^ in which glucose, lactose, and saccharose are 

 employed; (3) cultivation on Loeffler's blood serum and in gelatin stab culture; (4) 

 plate counts on sugar-free agar aerobically, and on lactose agar anaerobically; (5) the 

 use of Endo plates; (6) determination of spore-forming bacteria in lactose agar plates 

 and in milk tubes; and (7) employment of acetic acid glucose broth tubes for aciduric 

 organisms, 



Rettger and his associates^ had as their chief purpose the determination of the 



' Bunting, Nickerson, and Hard: Denial Cosmos, p. 931. Oct., 1926. 



^MacNeal, W. J., Latzer, L. L., and Kerr, J. E.: Joe. cit. 



3 Morris, G. B., Porter, R. L., and Meyer, K. V.: J. Infect. Dis., 25, 349. 1919. 



•> Herter, C. A., and Kendall, A. I.: /. Biol. Cliem., 10, 7, 203. 1909. 



5 Rettger, L. F., el at.: see various works cited [)re\'iously. 



