APPENDIX. 747 



gastric juice, since the curdling will take place in a neutral or alkaline 

 medium; neither does it depend upon the pepsin, as pure pepsin scarcely 

 curdles milk at all, and the rennet which rapidly curdles milk has a very 

 feeble proteolytic action. From this and other evidence it is believed 

 that a distinct milk-curdling ferment exists in the stomach. W. Roberts 

 has shown that a similar but distinct ferment exists in pancreatic extract, 

 which acts best in an alkaline medium, next best in an acid medium, 

 and worst in a neutral medium. The ferment of rennet acts best in an 

 acid medium, and worst in an alkaline, the reaction ceasing if the alka- 

 linity be more than slight. 



In addition to the above ferments, many others most likely exist in 

 the body, of which the following are the most important: 



(6.) Fibrin-forming ferment (Schmidt), (see p. 64, et seq.), found 

 in the blood, lymph and chyle. 



(7.) A ferment which converts glycogen into glucose in the 

 liver; being therefore an amylolytic ferment. 



(8.) Myosin ferment. 



(Z.) Organic non-nitrogenous bodies consist of 



(1.) OILS AND FATS. 



Most oils and fats are mixtures of palmitin C &1 H 90 6 , stearin C S7 - 

 H no 6 , and olein C 57 H 104 6 , in different proportions. They are formed 

 by the union of fatty acid radicals with the triatomic alcohol, Glycerin 

 C 3 H 5 (OH) 8 , and are ethereal salts of that alcohol. The radicals are C 18 - 

 H 35 0, C 16 H 31 0, and C I8 H 33 0, respectively. Human fat consists of a 

 mixture of palmitin, stearin, and olein, of which the two former con- 

 tribute three-quarters of the whole. Olein is the only liquid consti- 

 tuent. 



General characteristics. Insoluble in water and in cold alcohol; solu- 

 ble in hot alcohol, ether, and chloroform. Colorless and tasteless; easily 

 decomposed or saponified by alkalies or superheated steam into glycerin 

 and the fatty acids. 



Cholesterin, C 26 H 44 0, is the only alcohol which has been found in 

 the body in a free state. It has been called a non-saponifiable fat. It 

 occurs in small quantities in the blood and various tissues, and forms 

 the principal constituent of gall-stones. It is found in dropsical fluids, 

 especially in the contents of cysts, in disorganized eyes, and in plants 

 (especially peas and beans). It is soluble in ether, chloroform, or benzol. 

 It crystallizes in white feathery needles. See also under the head of the 

 constituents of the bile. 



Excretin (Marcet), and Stercorin (Flint), are crystalline fatty bodies 

 which have been isolated from the faeces. 



