DETERMINATION OF METABOLISM 147 



Autolysis. As a matter of fact, a great variety of enzymes, 

 not only lipases, but oxydases, reductases, etc., are demon- 

 strable in living tissues. No less than eleven ferments are said 

 to be active in the liver alone, namely, a proteolytic and a 

 nuclein-splitting ferment, a de-amidizing ferment, a fibrin 

 ferment, a milk-curdling ferment, a bactericidal ferment, an 

 oxidase, a lipase, a maltase, glycogenase, and an autolytic 

 ferment. When a piece of liver is removed with aseptic pre- 

 cautions and kept at body temperature, an extensive auto- 

 digestion occurs in which ammonia and other basic substances, 

 glycin, tryptophan, and tyrosin occur. Similar autolytic 

 changes occur in other tissues, in pathological growths like 

 carcinoma, and in the removal of such exudations as occur in 

 pneumonia. The ferments in certain cases have been obtained 

 in active condition in extracts. 



Urine. All the materials that enter the body and which 

 take a part in the complex interplay of chemical changes that 

 constitute living processes, sooner or later again leave the body 

 as waste products, i. e., they are excreted. By far the greater 

 part of these appear in the urine, in the expired air, and in the 

 feces. The carbon of the foodstuffs reappears chiefly in the 

 carbon dioxide of the expired air; the hydrogen, as water in 

 the urine, expired air, and perspiration, etc.; the nitrogen as 

 the nitrogenous bodies of the urine. 



The urine is the product of the secretory activity of the 

 kidney cells. It is a clear yellow liquid, acid to ordinary 

 indicators, but almost neutral by physicochemical tests. The 

 average specific gravity is 1020, with normal extremes from 

 1005 to 1035. The average quantity per day may be put 

 at 1200 c.c. to 1600 c.c., but it varies inversely with the activity 

 of the sweat glands. The composition of the urine is very 

 dependent upon the quantity and quality of food. The most 

 prominent constituents besides water and inorganic salts 

 are urea, uric acid, and allied purin bases, ammonia, hippuric 

 acid, kreatinin, etc. Also organic bodies indoxyl, phenyl, 

 skatoxyl, etc., conjugated with sulphuric acid. These conjugated 

 organic bodies are derived primarily from the digestive tract. 



Determination of Metabolism. It is a well-known fact 

 that in an adult the weight of the body may remain constant 

 for many years, even when the diet varies greatly in nature 



