1/ PHYSIOLOGICAL CHEMISTRY. 



are gas-forming organisms. The production of gas by the fecal 

 flora in dextrose-bouillon is subject to great variations under path- 

 ological conditions : alterations in the diet of normal persons will 

 also cause wide fluctuations. In this connection Herter has ob- 

 served a marked reduction or even complete cessation of gas pro- 

 duction by the mixed fecal bacteria while considerable doses of 

 benzoate were being given. A return to the former plane of gas 

 production followed the discontinuation of the benzoate. 1 Data 

 as to the production of gas are of considerable importance in a diag- 

 nostic way although the exact cause of the variations is not yet es- 

 tablished. It should be borne in mind in this connection that gas 

 volumes are frequently variable with the same individual. For 

 this reason it is necessary in every instance to follow the gas pro- 

 duction for a considerable period of time before drawing conclu- 

 sions. 2 



For diagnostic purposes the macroscopical and microscopical ex- 

 aminations of the feces ordinarily yield much more satisfactory data 

 than are secured from its chemical examination. 



EXPERIMENTS ON FECES. 



1. Macroscopical Examination. If the stool is watery pour 

 it into a shallow dish and examine directly. If it is firm or pasty 

 it should be treated with water and carefully stirred before the 

 examination for macroscopical constituents is attempted. 



The macroscopical constituents may be collected very satisfactor- 

 ily by means of a Boas sieve (Fig. 49, page 177). This sieve is 

 constructed of two easily detachable hemispheres which are held 

 together by means of a bayonet catch. In using the apparatus the 

 feces is spread out upon a very fine sieve contained in the lower 

 hemisphere and a stream of water is allowed to play upon it 

 through the medium of an opening in the upper hemisphere. The 

 apparatus is provided with an orifice in the upper hemisphere 

 through which the feces may be stirred by means of a glass rod 

 during the washing process. After 15-30 minutes washing noth- 

 ing but the coarse fecal constituents remain upon the sieve. 



2. Microscopical Examination. Watery stools should be placed 

 in a shallow dish, thoroughly mixed and a small amount removed 

 to a slide for examination. Stools of a firm or pasty consistency 

 should be rubbed up in a mortar with physiological salt solution 



1 Private communication from Professor C. A. Herter. 



2 Herter and Kendall : loc. cit. 



