414 



THE CHEMICAL COMPOSITION OF THE BODY [CH. XXVIII. 



hydrate molecule its formation from the latter is theoretically 

 possible. On the other hand, the opening of the inosite ring 

 would give rise to an open chain, and it has indeed been found 

 that lactic acid is formed from inosite by the action of certain 

 bacteria. 



The Pats. 



Pat is found in small quantities in many animal tissues. It is, 

 however, found in large quantities in three situations, viz., marrow, 

 adipose tissue, and milk. 



The contents of the fat cells of adipose tissue are fluid during life, 

 the normal temperature of the body (37 0., or 99 F.) being con- 

 siderably above the melting-point (25 C.) of the mixture of- the fats 

 found there. These fats are three in number, and are called palmitin, 

 stearin, and olein. They differ from one another in chemical com- 

 position and in certain physical characters, such as melting-point and 

 solubilities. Olein solidifies at 5 C., palmitin at 45 C., and stearin 

 at 53-65 C. It is thus olein which holds the other two dissolved at 

 the body temperature. Fats are all soluble in hot alcohol, ether, and 

 chloroform, but insoluble in water. 



Chemical Constitution of the Pats. The fats are compounds of 

 fatty acids with glycerin, and may be termed glycerides or glyceric 

 ethers. 



The fatty acids form a series of acids derived from the monatomic 

 alcohols by oxidation. Thus, to take ordinary ethyl alcohol, C 2 H 6 0, 

 the first stage in oxidation is the removal of two atoms of hydrogen 

 to form aldehyde, C 2 H 4 ; on further oxidation an atom of oxygen is 

 added to form acetic acid, C 2 H 4 2 . 



A similar acid can be obtained from all the other alcohols, 

 thus : 



From methyl alcohol 

 ethyl 

 propyl 

 butyl 

 amyl 

 hexyl 



CH 3 .HO, formic acid H.COOH is obtained 



C. 2 H 5 .HO, acetic 



CoH 7 .HO, propionic 



C 4 H 9 .HO, butyric 



C 5 H n .HO, valeric 



C 6 H 13 . HO, caproic 



CH 3 .COOH 

 , C 2 H 5 .COOH 

 , C,H 7 .COOH 

 , C 4 H 9 .COOH 

 , C 5 H n .COOH 



and so on. 



The sixteenth term of this series has the formula Ci 5 H 3 i.COOH, 

 and is called palmitic acid ; the eighteenth has the formula 

 Ci7H 35 .COOH, and is called stearic acid. Each acid, as will be 

 seen, consists of a radical, C 7i _iH 2u -iCO, united to hydroxyl 

 (OH). 



Oleic acid, however, is not a member of this series, but belongs 

 to a somewhat similar series known as the acrylic series, of which 



