532 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



include nucleins derived from the animal and vegetable cells in- 

 gested with food, which nucleins contain at least 8 per cent, of 

 phosphorus. We can now realize how great is the physiological 

 role of the pancreas and of the spleen in the organism. 



Indeed, the functions of these two organs may be said 

 to constitute one of the pillars upon which the vital functions 

 rest. As a constituent of calcium phosphate, phosphorus is 

 found in the bones, teeth, cartilage, and other tissues; in the 

 blood, milk, etc., in quantities which bespeak of its functional 

 prominence, since calcium phosphate is represented by nearly 

 six pounds among the organism's constituents. Sodium phos- 

 phate which gives the blood, lymph, and other body-fluids 

 their alkalinity and fluidity, and the potassium and magnesium 

 phosphates, which fulfill much the same role, obviously find 

 in phosphorus their main dynamic attributes. But it is when 

 we reach the nervous system that the functional worth of this 

 element reaches its highest mark. 



How are nervous structures neurons, axis-cylinders, 

 sheaths, etc. adequately supplied with blood-plasma, their 

 oxidizing substance, their phosphorus, etc.? 



THE PHYSIOLOGICAL CHEMISTRY OF NERVES. The func- 

 tions of myelin, or white substance of Schwann a jelly- 

 like homogeneous and transparent material which surrounds 

 the axis-cylinder of nerves, and is only separated from it by 

 a thin protoplasmic film may be said to be unknown. It 

 is a fatty substance, blackened by osmic acid, and which, 

 after death, coagulates and becomes opaque, loses its homo- 

 geneity, etc. Myelin is now universally considered as a pro- 

 tective coat: a function which the overlying neurilemma al- 

 ready fulfills. Is myelin fatty in the true sense of the word? 

 Examined chemically in quantities, a very large proportion of 

 dried nerve-substance about one-half, according to some ob- 

 servers consists of a peculiar body: cholesterin. This body 

 is not a fat, but an alcohol; like glycerin, however, which is 

 also an alcohol, it forms compounds with fatty acids. "Though 

 we do not know definitely the chemical condition in which 

 cholesterin exists during life in the medulla," says Professor 

 Foster, "it is more than probable that it exists in some com- 

 bination with some of the really fatty bodies also present in 



