APP.] CHEMICAL BASIS OF THE AXIMAL BODY. 743 



'as in the fats; and cetyl alcohol, or eethal, is obtained only from sperma- 

 ceti.) It is a white crystalline body, crystallising in fine needles from 

 its solution in aether, chloroform or benzol ; from its hot alcoholic solu- 

 tions it is deposited on cooling in rhombic tables. When dried it melts 

 at 145, and distils in closed vessels at 360 C. It is quite insoluble in 

 water and cold alcohol ; soluble in solutions of bile salts. 



Solutions of cholesterin possess a left-handed rotatory action on 

 polarised light, of - 32 for yellow light, this being independent of con- 

 centration and of the nature of the solvent 



Heated with strong sulphuric acid it yields a hydrocarbon ; with 

 concentrated nitric it gives cholesteric acid and other products. It is 

 capable of uniting with acids and forming compound aethers. 



Cholesterin occurs in small quantities in the blood and many tissue*, 

 and is present in abundance in the white matter of the cerebro- spinal 

 axis and in nerves. It is a constant constituent of bile, forming fre- 

 quently nearly the whole mass of some gall-stones. It is found in many 

 pathological fluids, hydrocele, the fluid of ovarial cysts, &c, 



Preparation. From gall-stones by simple extraction with boiling 

 alcohol, and treatment with alcoholic potash to free from extraneous 

 matter. 



As tests for this substance may be given : With concentrated sul-. 

 phuric acid and a little iodine a violet colour is obtained, changing 

 through green to red or blue. This is applicable to the microscopic 

 crystals. After dissolving in chloroform a blood-red solution is formed 

 on the addition of an equal volume of concentrated sulphuric acid; this 

 solution if exposed to the air in an open dish turns, blue, green and 

 finally yellow; the sulphuric acid under the chloroform has a green 

 fluorescence. After evaporation to dry ness with nitric acid, the residue 

 turns red on treating with ammonia. 



This body is described here rather for the sake of convenience than from its 

 possessing any close relationship to the substances immediately preceding. 



COMPLEX NITROGENOUS FATS. 



Lecithin. C H w NP0 9 . 



Occurs widely spread throughout the body. Blood, bile, and serous 

 fluids contain it in small quantities, while it is a conspicuous component 

 of the brain, nerves, yolk of egg, semen, pus, white blood-corpuscles, and 

 the electrical organs of the ray. 



When pure, it is a colourless, slightly crystalline substance, which 

 can be kneaded, but often crumbles during the process. It is readily 



