768 EXPERIMENT STATION RECORD. [Vol.43 



hifidxis and aaidopJiilus types are present. This in connection with a slight de- 

 crease in decomposition products seems to point out that lactose is an important 

 factor as a controlling agent in intestinal putrefaction. The l^est results, how- 

 ever, are obtained by using a milk diet in the form of fermented milk or sweet 

 whole milk. 



" One of the most striking facts to be noticed in the series of experiments Is 

 the characteristic change in the intestinal flora coupled with decreased intestinal 

 putrefaction whenever milk constituted a large part of the diet. In these cases 

 the intestinal flora changed from the usually Gram-negative coli type to one in 

 which the Gram-positive aciduric B. acidophilus was prominent. In all instances 

 where milk made up the principal part of the diet there was a marked decrease 

 in the decomposition products. 



" The first experiment deals with the germicidal efi:ect of lactic acid in milk. 

 Pathogenic bacteria introduced into milk cultures containing 1 per cent of lactic 

 acid were effectively checked and destroyed. This proves that lactic acid has 

 decided germicidal properties, and may prevent the infection of fermented milk 

 with harmful organisms. The results of the other experiments, however, seem 

 to indicate that this germicidal action of lactic acid does not extend to the 

 control of the organisms already in the intestine. 



" The results from the use of B. btilgaricus milk in connection with a regular 

 diet were very gratifying. Intestinal putrefaction decreased markedly when 

 at least; 2 qts. of bulgaricus milk were used and the other food reduced propor- 

 tionately. There was a general gain in weight, and those suffering from con- 

 stipation were very much relieved. Of special interest is the change in the in- 

 testinal flow. Notwithstanding the fact that very large numbers of B. hulgari- 

 Gus were ingested with the milk, only a few could be recovered from the feces. 

 B. bulgarictis is therefore not a natural inhabitant of the human intestinal tract. 

 The very closely related B. acidophihis could be found in large numbers, but 

 only after about 8 or 10 days' use of the Milgariciis milk. When milk was dis- 

 continued the B. acidophilus gradually disappeared, and the floi-a again showed 

 large numbers of the Gram-negative organisms. 



" The same held true with the whole sweet-milk experiment, which gave prac- 

 tically as good results as hulgaricxis milk. This fact becomes still more sig- 

 nificant when it is considered that B. acidophihis became a connnon Inhabitant 

 of the intestinal tract without the ingestion of the organism itself. This would 

 indicate that B. acidophilus is naturally an intestinal organism, and that its 

 presence or absence is dependent upon the nature of the food consumed. The 

 diet or nature of the food, then, is the controlling factor. The character of the 

 intestinal flora is dependent on, and alters with, the type of the food. The in- 

 gestion, then, of large numbers of certain bacteria without the proper diet can 

 be of little permanent value. This fact was brought out by the experiment in 

 which watery suspensions of B. bulgaricus, B. acidophilus, and B. bifidus were 

 consumed. The intestinal flora throughout the experiment showed large num- 

 bers of the Gram-negative types, and there was no appreciable decrease in the 

 decomposition products. 



" The use of lactose in bringing about decreased intestinal putrefaction gave 

 fair results, but they can not compare with the remarkable results obtained by 

 the use of bulgaricus or sweet milk. The beneficial effect of milk in the success- 

 ful treatment of vai-ious intestinal diseases, as typhoid fever, has for some time 

 been known to the medical profession, but not until recently has it been realized 

 that the explanation lay in its ability to change the intestinal flora from the 

 putrefactive type to the Gram-positive aciduric B. acidophilus group, the pres- 



