106 7HYSIOLOGICAL CHEMISTRY. 



variety of mucilaginous or oily looking drops and filaments, of double 

 contour, which exude from the edges of the mass, and remain separate 

 and ins.oluble ; resembling the microscopic forms produced under simi- 

 lar circumstances from the "myeline," or medullary layer of nerve 

 fibres. It is readily decomposed on standing, either in solution or in a 

 state of watery imbibition, acquiring an acid reaction. Decomposition 

 is also effected by acids or alkalies. By boiling with baryta-water 

 it suffers a characteristic alteration, giving rise to the production of 

 two new bodies ; namely, a nitrogenous alkaline substance and phos- 

 phoglyceric acid. 



As to the physiological character or significance of lecithine we are 

 entirely' in the dark, except in one respect. It is the only organic 

 combination in the body containing phosphorus. Considering the 

 many articles of food in which it is an ingredient, it must be intro- 

 duced, in no small quantity, with the nutriment ; and it certainly exists 

 abundantly in the substance of the nerves and nervous centres. But as 

 no known organic combination of phosphorus is discharged with the 

 excretions, this substance must pass out of the body as part of the 

 phosphates in the urine and the perspiration. On this account, together 

 with the fact of the constant consumption of oxygen by the animal 

 body, it is believed that the phosphorus, introduced as an ingredient of 

 organic materials, is converted in the system into phosphoric acid, and 

 appears finally under the form of phosphatic salts. 



2. Cerebrine, C 17 H3 3 NO 3 . 



As its name indicates, this is an ingredient of the brain and nerves, 

 the only parts of the body in which it is known to exist. Although not 

 yet obtained in a crystalline form, it is placed among the members of 

 this group because it resembles them in its general features of chemical 

 composition, particularly in its small proportion of nitrogen, and also 

 in certain reactions, which are entirely dissimilar to those of an albu- 

 minous matter. 



Cerebrine is insoluble in water, but if treated with boiling water it 

 swells, softens, and yields an emulsion. It is insoluble in cold alcohol 

 and ether, but soluble in boiling alcohol and ether, from which it is 

 again deposited on cooling. Boiling with baryta-water decomposes it 

 slowly and incompletely, and does not produce phosphoglyceric acid, 

 as cerebrine contains no phosphorus. If strongly heated in the air, it 

 turns brown, melts, and finally burns with a bright flame. 



It is much more abundant in the white than in the gray substance 

 of the brain, forming, according to Petrowsky, in the solid ingredients 

 of the white substance 9.5 per cent., in those of the gray substance 

 but little more than 0.5 per cent. It is undoubtedly a constituent of 

 the medullary layer of nerve fibres, but nothing is known of its origin, 

 metamorphoses, or physiological activity. 



