ROUTINE EXAMINATION OF FECES 117 



DIRECT MICROSCOPIC EXAMINATION OF FECAL 

 SUSPENSIONS 



Films were prepared from the standardized suspensions of fecal 

 specimens and stained by the Gram-method. The slides were counter- 

 stained with dilute carbol fuchsin. Such slides are of considerable value 

 in that they show the relative predominance of the different types of 

 bacteria, and emphasize in particular the conspicuous large Bacillus 

 acidophilus-like rods when they are present in any numbers. This 

 method has serious limitations, however, in that it does not give a true 

 picture of the viable organisms which are present in the intestinal tract. 

 Many of the rods and cocci that are seen in these preparations are dead 

 at the time of leaving the animal host, although they take one or the 

 other of the stains. Furthermore, such dead bacteria may continue 

 for considerable periods to be eliminated, owing to their being held back 

 in the folds and on the inner walls of the intestine. 



The results of the examination of stained films were recorded ver- 

 bally in the tables summarizing the data from the rat-feeding experi- 

 ments, while at the time the human subjects were employed they were 

 recorded in terms of percentage of Gram-positive and Gram-negative 

 organisms and Gram-positive rods and cocci. As will be seen in the 

 different tables these results correlated definitely with those obtained 

 by the use of whey agar plates and the Veillon tubes. The relative 

 numbers of aciduric organisms as compared with all other organisms 

 present in human feces were as a rule smaller by the direct than the 

 culture methods, and in many instances very considerably smaller. 

 In the examination of the rat feces, on the other hand, the direct count 

 was in perfect agreement quantitatively with the results of the other 

 two methods. In spite of the recognized limitations of this method, it 

 has proven itself to be indispensable in the present investigation. 



