116 TRANSFORMATION OF THE INTESTINAL FLORA 



to filling, one end of the tube is tightly plugged with a rubber stopper. 

 After filling, the other end is plugged with non-absorbent cotton. 



The Veillon tubes are filled about twelve centimeters deep with the 

 1.2 per cent whey agar described above, and sterilized in the autoclave. 

 The inoculation of the tubes was accomplished in the same way as the 

 agar tubes that are used for immediate plating. It is of much impor- 

 tance to mix the agar and inoculum thoroughly, and this is done best 

 by tilting the tubes back and forth somewhat vigorously, even though 

 the cotton plug becomes soiled. The formation of gas bubbles must be 

 avoided, however. The tubes are incubated for at least forty-eight 

 hours at 37° C. The colonies are examined with the aid of a hand lens 

 which magnifies at least four or five times. 



These tubes are well adapted for the study of both aerobic and 

 anaerobic organisms as well as the intermediate forms, as for example 

 B. bifidus. Furthermore, they present an excellent index of the presence 

 of gas-producing organisms found in the intestine, namely B. coli and 

 B. welchii, and of their relative numbers. For this purpose alone they 

 have been of inestimable value not only for the study of rat, but of 

 human feces as well. Gas-producing bacteria in rat feces are usually 

 relatively few, but in the stools of man they are as a rule very abun- 

 dant and it was feared at first that the agar would be so thoroughly 

 broken up as to make it impossible to study the individual colonies 

 with any degree of satisfaction. This obstacle is encountered in the 

 examination of ordinary (often termed "normal") feces of man, but in 

 direct proportion to the transformation that is brought about in the 

 intestinal flora by the agents which have been successfully employed in 

 this work, the number of gas-producing bacteria correspondingly 

 diminishes and often the tubes remain entirely free from gas in the 

 course of the experiments. 



Bacillus acidophilus is recognized in the Veillon tubes by the rather 

 small fuzzy or sea-urchin-like colonies which develop particularly well 

 in the upper and middle layers of the agar. Colonies of B. bifidus are 

 small, disc-like and smooth, and are most abundant in the three to six 

 centimeter layer which begins about one centimeter below the surface. 

 The colonies of the strict anaerobes make their appearance in the depth 

 of the agar. The different colonies may be reached for subculture study 

 and microscopic examination by removing the rubber stopper, drawing 

 or forcing the agar column out of the lower end of the tube, and fishing 

 with a platinum wire or a very fine-pointed pipette, or by filing and 

 breaking the tube in the immediate vicinity of the chosen colony. In 

 the present work almost the entire emphasis was placed on B. acidoph- 

 ilus colonies and gas production. These are indicated in the various 

 tables by the following signs: — , -+- — , +, H — h> H — I — h and -\ — | — | — h> 

 as has already been explained on page 12. (See Plate V.) 



