622 PHYSIOLOGICAL CHEMISTRY 



the entire volume of suspension by the Kjeldahl method 1 (see Chapter XXVII). 

 Also determine the total nitrogen in weighed portions of the original feces by the 

 Kjeldahl method. What percentage of the total nitrogen of the feces is bacterial 

 nitrogen? 



(6) If it is desired to determine the actual amount of nitrogen which is excreted 

 daily in the feces in the form of bacterial cells, proceed as follows : Ingest an ordi- 

 nary mixed diet for a period of three days. Separate the feces for this period accord- 

 ing to directions given on page 620, using charcoal for the first separation and car- 

 mine for the second or vice versa. Preserve the feces for the period according 

 to directions given on page 621. Mix the weighed feces thoroughly and analyze 

 for bacterial nitrogen and total nitrogen according to directions given elsewhere 

 (see Chapters XIV and XXVII). Calculate the actual output of bacterial nitrogen 

 per day and the percentage of the total nitrogen of the feces which was excreted 

 per day in the form of bacterial nitrogen. 



34. "Metabolic Product" Nitrogen in Feces. A certain quota of the fecal 

 nitrogen is due to the presence of residues of digestive secretions, epithelial cells, 

 bacteria, etc. The nitrogen in these forms has been called "metabolic nitrogen." 

 To determine this form of nitrogen one method 2 of procedure is as follows: Ingest 

 a non-nitrogenous diet for a period of two days. The diet may include desired 

 quantities of starch, cream, sugar, butler, water and sodium chloride. About 15 

 grams of agar-agar should be added to the diet to prevent constipation and to insure 

 the evacuation of approximately the normal quantity of feces. (For influence 

 of agar-agar see Experiment 35.) To separate the feces properly ingest a capsule 

 of carmine at the beginning of the test and one of charcoal at the end (see page 620). 

 Preserve the feces as described on page 621. After mixing the feces thoroughly 

 determine the nitrogen in weighed quantities by the Kjeldahl method 3 according 

 to directions given in Chapter XXVII. Calculate the quantity of nitrogen elimi- 

 nated per day. Inasmuch as no nitrogen was ingested the nitrogen present in the 

 feces is of metabolic origin, i.e., it is made up principally of nitrogen in the form of 

 cells, digestive secretions and bacteria. 



35. Influence of Indigestible Non-Nitrogenous Material upon 

 Fecal Output. This may be demonstrated by agar-agar ingestion. 

 This indigestible hemicellulose has the property of absorbing water 

 readily and therefore when ingested it increases the bulk of the feces 

 considerably. This fact is made use of in some forms of constipation 

 and in the determination of metabolic product nitrogen (see Experi- 

 ment 33). 



Experiment. Ingest a uniform diet for four days. Divide the interval into 

 periods of two days each, 4 and "separate" the feces by charcoal or carmine (see 

 Experiment 31). On the third and fourth days ingest 10 grams of agar-agar at 

 each meal. Collect the feces for each two-day period (see Experiment 31, 

 page 620), and note the increase hi the daily excretion under the influence of 

 the agar. ingestion. What was the increase per gram of agar? 



1 More accurate results will be secured if the bacterial nitrogen is determined on each 

 individual stool in the fresh condition. 



2 For a discussion of other methods of estimating metabolic product nitrogen see Forbes, 

 Mangels, and Morgan: Jour Agr. Res., Q, 405, 1917. 



1 In the oxidation process use 10 grams of potassium sulphate instead of the copper 

 sulphate. The remainder of the procedure is the same as for urine. 

 4 Longer periods are desirable where great accuracy is desired. 



