2o6 TEXT-BOOK OF PHYSIOLOGY 



is in part absorbed into trie portal blood and carried direct to the liver where 

 it is oxidized to indoxyl and combined or conjugated with potassium sulphate 

 forming the salt potassium indoxyl sulphate or indican, after which it enters 

 the blood, is carried to and eliminated by the kidneys. The presence of this 

 salt in the urine can be demonstrated by adding hydrochloric acid with a 

 small quantity of potassium chlorate; after this is done the indican combines 

 with water and undergoes a cleavage into indoxyl and potassium sulphate; 

 the former then combines with oxygen and gives rise to indigo blue. The 

 extent to which the indican is present is taken as a measure of the extent of 

 intestinal putrefaction. 



Skatol. This compound is also a derivative of the protein molecule, the 

 result of bacterial decomposition. It passes in part into the feces and gives 

 to them the characteristic odor. It is also in part absorbed into the portal 

 blood and carried direct to the liver where it is oxidized to skatoxyl, after 

 which it combines with potassium sulphate to form potassium skatoxyl sul- 

 phate after which it .enters the blood and is carried to the kidneys to be elimi- 

 nated in the urine. 



Phenol and Cresol. These compounds, also derivatives of the protein 

 molecule, are absorbed into the portal blood and undergo a similar conjuga- 

 tion. They too are finally eliminated by the kidneys. 



The Feces. The feces is a term applied to the mass of material ejected 

 from the rectum through the anus. They are characterized by consistency, 

 color and odor. The origin and the nature of this material have both a 

 physiologic and a clinic interest. 



The consistency varies from day to day from liquid to solid, depending 

 partly on the character of the food, the rapidity with which it is transported 

 through the intestine and hence the extent to which absorption of water in 

 the large intestine takes place. On a meat diet the consistency is firm; on a 

 vegetable diet it is apt to be soft. The amount discharged from day to day 

 on a mixed diet varies from 120 to 170 grams containing from 30 to 42 grams 

 of dry matter. On a meat diet alone the quantity diminishes; on a vege- 

 table diet, especially if the articles of food are rich in cellulose, the quantity 

 will increase considerably beyond the customary amount. 



The color on a mixed diet varies from a light yellow to black. The 

 usual brown color is due to the pigment urobilin or stercobilin, a derivative 

 of the pigments of the bile. On a meat diet the color deepens until it becomes 

 quite black due to the presence of sulphid of iron, the result of the union 

 of sulphuretted hydrogen with the iron derived from hematin contained in 

 the meat. On a vegetable diet the color lightens and may become slightly 

 yellow. If the contents of the intestine are carried forward too rapidly, the 

 time may be insufficient for a complete reduction of the bile pigments, hence 

 they appear in the feces imparting to them a green color. If there is an 

 obstruction to the discharge of bile into the intestine the feces may become 

 yellow or clay-colored. 



The odor is characteristic and due to the presence of skatol and allied 

 bodies produced by the putrefaction of proteins by bacterial action. Sul- 

 phuretted hydrogen also contributes to the odor. 



The chemic composition of the feces is complex. They consist of water, 

 mucin, an indigestible residue of food, decomposition products, excretions 

 from the intestinal glands, and inorganic salts. The residue of the food 



