340 HAND-BOOK OF PHYSIOLOGY. 



Formic, acetic, and propionic acids are present in sweat, but normally 

 in no other human secretion. They have been found elsewhere in dis- 

 eased conditions. Butyric acid is found in sweat. Various others of 

 these acids have been obtained from blood, muscular juice, faeces, and 

 urine. 



Group II. Diatomic Fatty Acids. 



Monobasic. 



Glycolic C 2 H 4 3 



Lactic C 3 H 6 3 



Leucic C 6 H 12 3 



Bibasic. 



Oxalic C 2 H 2 O 4 



Succinic C 4 H 6 O 4 



Sebacic 10 H 10 O 4 



Lactic acid exists in a free state in muscular plasma, and is increased 

 in quantity by muscular contraction, is never contained in healthy blood, 

 and when present in abnormal amount seems to produce rheumatism. 



Oxalates are present in the urine in certain diseases, and after drink- 

 ing certain carbonated beverages, and after eating rhubarb, etc. 



AROMATIC SERIES. 



Benzoic C 7 H 6 2 



Phenol . . . . C 6 H 6 



Benzoic acid is always found in the urine of herbivora, and can be 

 obtained from stale human urine. It does not exist free elsewhere. 



Phenol. Plienyl alcohol or carbolic acid exists in minute quantity in 

 human urine. It is an alcohof of the aromatic series. 



2. INORGANIC PRINCIPLES. 



The inorganic proximate principles of the human body are numerous. 

 They are derived, for the most part, directly from food and drink, and 

 pass through the system unaltered. Some are, however, decomposed on 

 their way, as chloride of sodium, of which only four-fifths of the quantity 

 ingested are excreted in the same form; and some are newly formed 

 within the body, as for example, a part of the sulphates and carbonates, 

 and some of the water. 



Much of the inorganic saline matter found in the body is a necessary 

 constituent of its structure, as necessary in its way as albumin or any 

 other organic principle; another part is important in regulating or modify- 

 ing various physical processes, as absorption, solution, and the like; while 

 a part must be reckoned only as matter, which is, so to speak, accident- 

 ally present, whether derived from the food or the tissues, and which 

 will, at the first opportunity, be excreted from the body. 



Gases. The gaseous matters found in the body are Oxygen, Hydro- 



