THE CHEMICAL CONSTITUTION OF THE ANIMAL BODY. 139 
They are all composed of C, H, N,O. Chondrin, gelatin, 
ceratin have, in addition, S. 
Chondrin: The organic basis of cartilage. Its solutions 
set into a firm jelly on cooling. 
Gelatin: The organic basis of bone, teeth, tendon, etc. Its 
solutions set (glue) on cooling. ~ 
Elastin: The basis of elastic tissue. Its solutions do not set 
jelly-like (gelatinize). 
Mucin: From the secretion of mucous membranes; precipi- 
tated by acetic acid, and insoluble in excess. 
Keratin: Derived from hair, nails, epidermis, horn, feathers. 
Highly insoluble. 
Nuclein: Derived from the nuclei of cells. Not digested 
by pepsin; contains P but no 8. 
THE FATS. 
The fats are hydrocarbons; are less oxidized than the carbo- 
hydrates; are inflammable; possess latent energy in a high 
degree. 
Chemically, the neutral fats are glycerides or ethers of the 
fatty acids, i.e., the acid radicles of the fatty acids of the oleic 
and acetic series replace the exchangeable atoms of H in the 
triatomic alcohol glycerine, e. g.: 
Glycerine. Palmitic acid. Glycerine tripalmitate or palmitin. 
OH HO.0C.C,;Ha 0.CO.CisHa 
C.H; OH + HO.OC.C,;Ha = CsHs 0.CO.C;;Ha + 3H,0 
OH 4HO0.0C.C,Ha 0.CO.C,sHa 
A soap is formed by the action of caustic alkalies on 
fats, e. g.: 
Tripalmitin. Potassium palmitate. 
(Cuba) f+ 9 KOH) = 3} (eA) OF +a 0. 
The soap may be decomposed by a strong acid into a fatty 
acid and glycerine, e. g.: 
CisHs.CO.K + HCl = C,;Hs.CO.H + KCl. 
Potassium palmitate. Palmitic acid. 
The fats are insoluble in water, but soluble in hot alcohol, 
ether, chloroform, etc. 
The alkaline soaps are soluble in water. 
