III. FEEDING AND IMPLANTATION EXPERI- 

 MENTS WITH HUMAN SUBJECTS 



The following experiments followed closely upon those which were con- 

 ducted on white rats and which form the subject matter of the pre- 

 ceding chapter. Very little difficulty .was experienced in procuring 

 volunteers, most of whom were graduate students and assistants in the 

 laboratory. Thus far in the investigation seventeen human subjects 

 have been employed of which fifteen were apparently normal and two 

 had a long history of intestinal disturbances. Altogether 600 stools 

 were examined. Most of the subjects served in more than one experi- 

 ment, bringing the total number of individuals up to forty-six. 



The attempts to duplicate the results obtained with white rats were 

 in a very large measure successful. The investigation resolved itself 

 into numerous phases in almost all of which the chief aim was to 

 establish a Bacillus acidophilus flora in the intestinal tract, either by 

 the administration, in conjunction with the ordinary daily diet, of 

 special carbohydrates, namely lactose and dextrin, or of living and 

 viable cultures of B. acidophilus in whey broth or in milk, or of a com- 

 bination of either of these carbohydrates with the living cultures. 



Following a brief period of preliminary observation, and after several 

 bacteriological examinations of the stools had been made, the subjects 

 entered upon a period of daily administration of the above-mentioned 

 test materials, which usually extended over ten days, and in some 

 instances twenty and thirty days. The feces were collected in paraffined 

 paper containers, and immediately brought to the laboratory where 

 they were placed in the refrigerator, and examined on the same day. 

 Daily examinations were made, the technique being essentially the same 

 as that employed in connection with the feeding experiments on rats 

 except that the fecal suspensions for the inoculation of whey agar for 

 plating and of the Veillon tubes were made up to match tubes ten to 

 twelve of the nephelometer scale, instead of eight, and that the bacteria 

 on the Gram-stained slides were counted and the numbers of the different 

 types given in terms of percentage. The greater turbidity was found 

 desirable owing to the decidedly smaller number of viable bacteria 

 present in human as compared with rat feces. 



The various tables indicate a fairly close correlation between the 

 results obtained through cultural procedures and- the direct counts of 

 the Gram-stained films prepared from the fecal suspensions. The 



