PREFACE 



Fifty years have passed since Pasteur and Koch, the founders of 

 modern bacteriology, made their first contributions to this new field 

 of scientific study. No phase of the subject has been given more atten- 

 tion by investigators than the bacteriology of the digestive tract. 

 However, success in these endeavors has been limited, with few excep- 

 tions, to the discovery of microorganisms which are manifestly disease- 

 producing and which exert their baneful influence in comparatively short 

 periods of time, as for example the microbial agents causing typhoid 

 fever and epidemic dysentery. The more subtle bacterial processes 

 which take place in the intestine, and the laws which govern the pre- 

 ponderance of one type of bacteria over another, have as yet been but 

 little understood. 



The authors have aimed to present here in as direct a manner as 

 possible the results of an extended series of observations on: (1) the 

 relation of diet to the character of the intestinal bacterial flora, and 

 (2) the possibility of implanting bacteria of known physiological prop- 

 erties in place of those which ordinarily hold sway after early infancy. 



The demonstration that lactose, dextrin and milk, when taken in suf- 

 ficient amount, encourage a non-putrefactive flora, and that a non- 

 putrefactive organism like Bacterium acidophilus may be established 

 in the intestine by oral administration, should be of fundamentally 

 scientific interest, irrespective of any important bearing that it may 

 have on the many and complex problems related to intestinal disease 

 and minor alimentary disturbances. 



The descriptions of methods employed in the examination of fecal 

 specimens are given in some detail for the use of other investigators 

 who are engaged in studies similar to those recorded in this treatise. 

 Particular attention is given also to the preparation and use of Bac- 

 terium acidophilus milk, since the experience of the last six months has 

 shown that the administration of this product is the most effective and 

 practical method of implanting the submissive aciduric organism in the 

 digestive tract, and one which is not only well-borne by the subject but 

 is as a rule welcomed by him because of its unique qualities as a beverage 

 and a real food. 



The Authoes. 



New Haven, Conn., October, 1920. 



