510 ACIDS AND ALCOHOLS. 



One of its compounds, glycin (glycocoll, amidoacetic acid, or gelatin-sugar), occurs 

 as a conjugate acid, viz., as glycocholic acid in the bile (p. 355), and as hippuric 

 acid in the urine. Glycin exists in complex combination in gelatin. 



(c.) Lactic Acid (oxy-propionic acid), C 3 H 4 (OH) 2 , occurs in the body in two 

 isomeric forms 1. The ethylidene-lactic acid, which occurs in two modifications 

 as the right rotatory sarcolactic acid (paralactic), a metabolic product of muscle ; 

 and as the ordinary optically inactive product of "lactic fermentation," which 

 occurs in gastric juice, in sour milk (sauerkraut, acid cucumber), and can be 

 obtained by fermentation from sugar (p. 373). 2. The isomer, ethylene-lactic acid, 

 occurs in the watery extract of muscles. 



(d.) Leucic acid (oxy-caproic acid), CgH^Og, does not occur as such, but only in 

 the form of one of its derivatives, leucin (amido-caproic acid), as a product of the 

 metabolism in many tissues, and is formed during pancreatic digestion (p. 342). 

 Leucic acid may be prepared from leucin, and glycolic acid from glycin by the 

 action of nitrous acid. 



(4.) Acids of the Oxalic Acid or Succinic Acid Series having the formula, 

 C n H 2n _40 2 (OH)2, are bi-basic acids, which are formed as completely oxidised 

 products by the oxidation of fatty acids and glycolic acid (H 2 being removed); 

 and it is important to note their origin from substances rich in carbon, e.g., fats, 

 carbohydrates, and proteids. 



(a.) Oxalic Acid, C 2 2 (OH) 2 , arises from the oxidation of glycol, glycin, 

 cellulose, sugar, starch, glycerine, and many vegetable acids it occurs in the 

 urine as calcium oxalate. 



(b.) Succinic Acid, C 4 H 4 2 (OH) 2 , has been found in small amount in animal 

 solids and fluids; spleen, liver, thymus, thyroid; in the fluids of echinococcus, of 

 hydrocephalus, and of hydrocele, and more abundantly in dog's urine after fatty 

 and flesh food; in rabbit's urine after feeding with yellow turnips. It is also 

 formed in small amount during alcoholic fermentation (p. 298). 



(5.) CholallC Acids in the bile (p. 35G) and in the intestine (p. 367). 



(6.) Aromatic Acids Benzole acid (= phenyl-formic acid) occurs in urine 

 united with glycin, as hippuric acid (see Urine). 



Ill Alcohols. 



Alcohols are those bodies which originate from carbohydrates, in which the 

 radicle hydroxyl (HO) is substituted for one or more atoms of H. They may be 



TT "I 



regarded as water, T \ 0, in which the half of the H is replaced by a CH com- 



/~1 TT -V 



pound. Thus, C 2 H G (ethyl-hydrogen) passes into 2 T| \ (ethylic alcohol). 



C TT 1 

 (a.) Cholesterin, 2G T? j-0, is a true men-atomic alcohol, and occurs in blood, 



yelk, brain, bile (p. 358), and generally in vegetable cells. 



I OH 



(6.) Glycerine, C 3 H 5 < OH, is a tri-atomic alcohol. It occurs in neutral fats 



(OH 



united with fatty acids and oleic acid ; it is formed by the splitting-up of 

 neutral fats during pancreatic digestion (p. 343), and during the alcoholic fermen- 

 tation (p. 298). 



(c.) Phenol (= phenylic acid, carbolic acid, oxybenzol, p. 376). 



(d.) BrenzTcatecliin ( = dioxybenzol). 



(e.) The Sugars are closely related to the alcohols, and they may be regarded 

 as polyatomic alcohols. Their constitution is unknown. Together with a series 

 of closely-related bodies they form the great group of the Carbohydrates, some 

 of which occur in the animal body, while others are widely distributed in the 

 vegetable kingdom. 



