CHANGES IX INTESTINES. THE FECES. 2OI 



The high nitrogen of No. Ill indicates an excess of pro- 

 tein ; this being high, the fat and ash must be correspondingly 

 low. The difference in the two kinds of feces becomes more 

 apparent when it is remembered that a much higher factor 

 must be used in multiplying the N values to obtain original 

 substance in III than is probable for I and II. Since in III 

 an excess of protein is known to be present the factor ap- 

 proaches 6.25, while for I and II it is probably not over 4.5 

 or 5.0. Something will be said below about the general char- 

 acter of the important fat and nitrogen substances present in 

 the feces. 



THE ANALYSIS OF FECES AND INTERPRETATION OF RESULTS. 



This may extend to the recognition of a large number of 

 products, but usually includes the detection and determination 

 of a few important ones only. Fat of some kind is always 

 present, hence a qualitative test is of little value. The total 

 amount of fat must be determined by some kind of an extrac- 

 tive process. Nitrogen is determined generally by the Kjel- 

 dahl method and special tests are made for proteins or their 

 more immediate derivatives. Occasionally unchanged starch 

 and other carbohydrates are present which may be recognized 

 by methods given below. The amount and character of the 

 ash is sometimes of value, likewise the reaction. Below a few 

 details will be given about some of these tests. 



Separation. Ordinarily tests are made on feces of mixed 

 diets, but frequently it is desirable to observe the character of 

 feces following special diet and not modified by the product 

 from a previous or later diet. To separate the feces for such 

 tests several schemes have been proposed. It is best to give 

 some inert substance at the beginning of the period which will 

 pass through the stomach and intestines unchanged, and at 

 the conclusion of the period of dieting the same subsl 



