THE CHARACTERISTICS OF BACTERIA OF THE COLON 

 TYPE OCCURRING IN HUMAN FECES 



L A. ROGERS, WILLIAM MANSFIELD CLARK and HERBERT A. LUBS 



Research Laboratories of the Dairy Division, Bureau of Animal Industry, United 

 States Department of Agriculture^ 



Received for publication April 25, 1917 

 INTRODUCTION 



The great value to sanitary science of a knowledge of intestinal 

 bacteria has stimulated investigation on the colon group until 

 an extensive literature on this subject has accumulated. The 

 striking character of the group is its activity in fermenting carbo- 

 hydrates and on this most of the attempts at classification have 

 been based. Unfortunately, inexact methods of demonstrating 

 and measuring complicated physiological processes have de- 

 tracted from the value of some of this work. The fermentation 

 of carbohydrates by microorganisms is evidently a much more 

 complicated process than was formerly supposed. The inter- 

 mediate and end products are subject to no little variation 

 under the influence of the conditions of the fermentation. Con- 

 clusions based on inexact methods are necessarily open to 

 question. This is particularly well illustrated by the history 

 of the Smith fermentation tube, the limitations of which were 

 better recognized by its originator than by many who have 

 followed him in its use. At first great dependence was placed 

 on the volume of gas evolved and the relative percentage of 

 hydrogen and carbon dioxide produced, as determined without 

 taking into consideration the dissolved gas. The results ob- 

 tained by these methods were so erratic that the fermentation 

 tube has come to be used merely for the determination of fer- 

 mentation and the variations in the volume and ratio of gases 



^ Published by permission of the Secretary of Agriculture. 



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