ORGANIC ELEMENTS. 53 



It is solid; pulverulent; when dry, insipid, inodorous, and heavier than 

 water. When decomposed by heat, it yields carbonate of ammonia, 

 charcoal, &c. It is insoluble in water, alcohol, and the oils; but solu- 

 ble in alkalies. On the gradual addition of nitric acid to a fluid, which 

 contains this substance in solution, a very characteristic series of tints 

 is evolved. The fluid becomes first blue, then green, afterwards vio- 

 let and red, and ultimately assumes a yellow or yellowish-brown colour. 



On adding an acid to a solution of biliphsein, a precipitation of green 

 flocculi takes place : these possess all the properties of chlorophyll, or 

 the green colouring matter of leaves. In this state it is termed bili- 

 verdin by Berzelius ; and is a product of the metamorphosis of bili- 

 phsein. 1 



These are the chief nitrogenized organic elements. 



b. Organic Elements that do not contain Nitrogen. 



1. Olein and Stearin. Fixed oils and fats are not pure proximate 

 principles, as was at one time supposed. They were Jong presumed 

 to consist of two substances, one of which is solid at the ordinary tem- 

 perature of the atmosphere, and the other fluid : the former of these 

 was called Stearin, from of tap, suet ; the latter Ela'in or Olein, from 

 jT-atov, oil. Stearin is the chief ingredient of vegetable and animal 

 suet ; of fat and butter ; and is found, although in small quantity, in 

 fixed oils. In suety bodies, it is the cause of their solidity. Elain 

 and stearin may be separated from each other by exposing fixed oil to 

 a low temperature ; and pressing it, when congealed, between folds of 

 bibulous paper. The stearin is thus obtained in a separate form ; and 

 by pressing the bibulous paper under water, an oily matter is procured, 

 which is elain in a state of purity. Modern chemistry has shown, 

 however, that fat contained in the cells of adipose tissue is composed 

 of a base termed glycerin itself hydrated oxide of glyceryl with 

 stearic and margaric acids. Stearin is a bi-stearate of glycerin: 

 olein, or elain, an oleate of glycerin. 



2. Fatty matter of the Brain and Nerves. Yauquelin 2 found two 

 varieties of fatty matter in the brain, the one white, the other red, 

 the properties of which have not been fully investigated. Both give 

 rise to phosphoric acid by calcination, without there being any evidence 

 of an acid, or phosphate in their composition. They may be obtained 

 by repeatedly boiling the cerebral substance in alcohol ; filtering each 

 time; mixing the various liquors, and suffering them to cool: a lamel- 

 lated substance is deposited, which is the white fatty matter. By eva- 

 porating the alcohol, which still contains red fatty matter and osmazome, 

 to the consistence of bouillie; and exposing this, when cold, to the 

 action of alcohol, the osmazome is entirely dissolved, whilst the alcohol 

 takes up scarcely any red fatty matter. 



3. Acetic acid. This acid exists in a very sensible manner in sweat, 

 urine, and milk even when entirely sweet. It, or lactic acid, is formed 

 in the stomach in indigestion ; was found by the author and his late 

 friend, Professor Emmet, contained in the gastric secretions in health, 



1 Simon, op. cit., p. 44. a Annales de Chim., Ixxxi. 37. 



