1000 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



in the urine. He therefore concludes that the oxalic acid in the urine is 

 derived from the oxalates of the food and not from metabolism in the body. 

 Stones in the bladder are sometimes composed of calcium oxalate, as are also 

 urinary sediments when formed in consequence of ammoniacal fermentation. 



Succinic Acid, HOOC.C 2 H 4 .COOH. This has been detected in the 

 spleen, thymus, thyroid, in echinococcus fluid, and often in hydrocele fluid. It 

 is a product of alcoholic fermentation, and of proteid putrefaction. It is often 

 found in plants. 



Amido-succinic Acid, or Aspartic Acid, HOOC.C 2 H 3 NH 2 .COOH. 

 This is a product of boiling proteid with acid or alkalies, and it is also formed 

 under the influence of trypsin in proteid digestion. 



Monamide of Amido-succinic Acid, or Asparagin, H 2 NOC.C 2 H 3 NH. 2 .COOH. 



This is found widely distributed in plants, especially in the germinating seed. If a plant 

 be placed in the dark its proteid nitrogen decreases, whereas the non-proteid nitrogen 

 increases, 1 the cause of this being attributed to proteid metabolism with the production of 

 amido- acids, i. e. aspartic and glutamic acids, leucin, and tyrosin. In the sunlight, it 

 is believed, these bodies are later reconverted into proteid. One view regarding the for- 

 mation of asparagin is based theoretically on the production of succinic acid from carbo- 

 hydrates (as in alcoholic fermentation) and the subsequent formation of oxysucdnic acid 

 (or malic acid, HOOC.C 2 H 3 OH.COOH), which the inorganic nitrogenous salts change 

 to asparagin. 2 At any rate asparagin in the plant has the power of being constructed into 

 proteid. Since proteid in the animal body may yield 45 per cent, of dextrose in its 

 decomposition, as will be shown, it seems fair to surmise that the synthesis of proteid in 

 the plant may in part depend upon the union of asparagin or similar amido- compounds 

 with the carbohydrates present. Asparagin if fed is converted into urea. It forms no 

 proteid synthesis in the animal, and has only a very small effect as a food-stuff. 3 



Glutamic acid, HOOC.CHNH 2 .CH 2 .CH 2 .COOH. This is found as a cleavage- 

 product of tryptic digestion in the intestinal canal. Glutamin, its amido- compound, is, like 

 asparagin, widely distributed in the vegetable kingdom and in considerable amounts. It 

 probably plays the same role as asparagin in the plant. Grlutamin is more soluble than 

 asparagin and is therefore less easily detected. 



COMPOUNDS OF TRIATOMIC ALCOHOL RADICALS. 



Glycerin, or Propenyl Alcohol, CH 2 OH.CHOH.CH 2 OH. The glycerin 

 esters of the fatty acids form the basis of all animal and vegetable fats. 

 Glycerin is furthermore formed in small quantities in alcoholic fermentation. 



Preparation. (1) Through the action of an alkali on a fat, glycerin and a 

 soap are formed, a process called saponification : 



2C 3 H 5 (C 18 H 35 2 ) 3 + GNaOH - 2C 3 H 5 (OH) 3 



Stearin. Sodium stearate. 



(2) Fats may be decomposed into glycerin and fatty acid by superheated 

 steam, and likewise by the fat-splitting ferment in the pancreatic juice. Thus, 

 if a thoroughly washed butter-ball, consisting of pure neutral fat, be colored 

 with blue litmus, and a drop of pancreatic juice be placed upon it, the mass 



1 Schulze and Kisser : Landwirthschatfliche Versuchs-Station, 1889, Bd. 36, p. 1. 



2 Miiller: Ibid., 1886, Bd. 33, p. 326. 



8 See Voit : Zeitschrift fur Biologie, 1892, Bd. 29, p. 125. 



