242 PHYSIOLOGICAL CHEMISTRY. 



but contains somewhat less water. The organic substance yields 

 gelatine on boiling; but the dental tubes are not dissolved, there- 

 fore they cannot consist of collagen. In dentin 260-280 p. m. 

 organic substance has been found. Enamel is an epithelium for 

 mation containing a large proportion of lime-salts. The fact that 

 the organic substance of enamel does not yield any gelatine corre- 

 sponds to its nature and origin. Completely-developed enamel 

 contains the least water, the greatest quantity of mineral sub- 

 stances, and is the hardest of all the tissues of the body. In full- 

 grown animals it contains hardly any water, and the amount of 

 organic substance amounts to only 20-40 p. m. The relative 

 amounts of calcium and phosphoric acid are, according to the 

 analyses of HOPPE-SEYLER, about the same as in bone-earths. 

 According to the determination of BERZELIUS, the enamel may 

 contain 40 p. m. calcium fluoride. 



IV. The Fatty Tissue. 



The membranes of the fat-cells withstand the action of alcohol 

 and ether. They are not dissolved by acetic acid nor by dilute 

 mineral acids, but are dissolved by artificial gastric juice. They 

 may possibly consist of a substance closely related to elastin. The 

 contents of the fat-cells are fluid during life, but solidify after 

 death and become more or less solid, depending upon the charac- 

 ter of the fats. Besides fat, the fat-cells contain a yellow pigment 

 which in emaciation does not disappear so rapidly as the fat; and 

 this is the reason that the subcutaneous cellular tissue of an ema- 

 ciated corpse has a dark orange-red color. The cells deficient in 

 or nearly free from fat, which remain after the complete disappear- 

 ance of the latter, seem to have an albuminous protoplasm rich in 

 water. 



The less water the fatty tissue contains, the richer it is in fat. 

 SCHULTZE and KEINECKE found in 1000 parts : 



Water. Membrane. Fat. 



Fatty tissue of oxen 99.6 11.6 888.8 



" "sheep 104.8 16.4 878,8 



" "pigs 64.4 13.5 922.1 



