FECES 227 



carbohydrate the field is strongly Gram positive and has a more homo- 

 geneous appearance. The bacteria seen consist chiefly of long slender 

 Gram-positive rods -belonging to the B. acidophilus and B. bifidus 

 groups. 1 



The nitrogen present in the feces consists principally of bacteria, 

 unabs orbed intestinal secretions, epithelial cells, mucus material and food 

 residues. In the early days of nutrition study the fecal nitrogen was 

 believed to consist principally of food residues. We now know that 

 such residues ordinarily make up but a small part of the nitrogen quota 

 of the stools of normal individuals who exercise normal mastication. 2 

 When meat has been "bolted," however, from J^ gram to 16 grams of 

 macroscopical meat residues has been found in a single stool. 3 The 

 phrase " metabolic product nitrogen" is frequently used as a designa- 

 tion for all fecal nitrogen except that present as food residues and 

 bacteria. Bacteria cannot logically be classed under " metabolic" 

 nitrogen since they doubtless develop at the expense of food nitrogen 

 as well as at the expense of that in the form of intestinal secretions. 

 In the accurate study of "protein utilization" 4 a correction should be 

 made for "metabolic nitrogen." Data regarding the output of meta- 

 bolic nitrogen may be secured by determining the fecal nitrogen excre- 

 tion on a diet of proper energy value but containing no nitrogen* 

 Agar-agar may be utilized advantageously in connection with such a 

 nitrogen-free diet. 



Feces are still excreted from the intestine even when no food is 

 ingested. Carefully conducted fasting experiments have demonstrated 

 this. A dog nourished on an ordinary diet to which bone ash has been 

 added will excrete a grey feces. When fasted such an animal will, after 

 a few days, excrete a small amount of a greenish-brown mass, containing 

 no bone ash. These are fasting feces. It is of a pitch-like consistency 

 and turns black on contact with the air. 6 Adult fasting men have been 

 found to excrete 7-8 grams of feces per day, the daily nitrogen value 

 being about o.i gram. 7 No separating medium such as charcoal or 

 carmine (page 238) should be used in differentiating fasting feces. 



In recent years the examination of feces for evidences of parasitism 

 (detection of parasites and their ova) has taken on an added importance. 

 The investigation of the hookworm has been particularly developed. 



^ammidge: The Feces of Children and Adults, 1914, p. 126. 



2 Kermauner: Zeit. fiir BioL, 35, 316, 1897. 



3 Foster and Hawk : Jour. Am. Chem. Soc., 37, 1347, 1915. 



4 The percentage of the ingested protein which is absorbed from the intestine. This 

 may be calculated by subtracting the metabolic nitrogen from the total fecal nitrogen and 

 dividing this value by the food nitrogen. 



5 Tsuboi: Zeit. fur BioL, 35, 68, 1897; Mendel and Fine: Jour. Biol. Chem., n, 5, 1912. 



6 Howe and Hawk: Jour. Am. Chem. Soc., 33, 215, 1911. 



7 Howe, Mattill and Hawk: Ibid., 33, 568, 1911. 



