534 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



is accompanied by the liberation of heat, the presence of which 

 Schiff has demonstrated even up to the nerve-centers, under 

 the influence of fear, of excitation of the senses, of any cause 

 in a word which produces cerebral activity." 



Lecithin "a conspicuous component of the brain, nerves, 

 yelk of egg, semen, pus, white blood-corpuscles, and the elec- 

 trical organs of the ray" suggests its identity as at least one 

 of the sources of energy we are seeking by the fact that if 

 merely allowed to stand at the ordinary temperature its solu- 

 tions acquire an acid reaction and are decomposed. In the 

 intestines it sometimes breaks up into its constituents: fatty 

 acids, glycerin, phosphoric acid, and cholin (Ho well). Neurin 

 is, in reality, cholin, and therefore a decomposition product of 

 lecithin. As previously stated, Tappeiner 31 obtained fatty acids 

 as a result of cholic-aeid oxidation. These facts, of course, are 

 only cited as mere landmarks to indicate that we are dealing 

 with oxidizable bodies. As far as the nerves themselves are 

 concerned, therefore, it seems probable that we have in lecithin 

 an agency capable, by the character of its molecule, i.e., car- 

 bohydrates, phosphorus, etc., of acting as a potent source of 

 working energy when brought into contact with the oxidizing 

 substance; and in cholesterin the main waste-product of nerve- 

 catabolism. 



Admitting, then, that we have in the lecithin of myelin 

 a body capable of acting as a source of energy in a way similar 

 to myosinogen in muscle, how does the oxidizing substance of 

 the blood-plasma reach it? The nodes of Ranvier and the 

 neurilemma that covers them allows silver stains to reach the 

 axis-cylinder, but the myelin itself does not permit of this. 

 This suggests that the nodes themselves i.e., the rings form- 

 ing them may allow the blood-plasma to filter through them, 

 thus bringing the oxidizing substance in immediate contact 

 with the axis-cylinder. The finer anatomy of nerves indicates 

 that such may be the case. Indeed, the nodes referred to occur 

 at regular intervals, and separate the nerve, as is well known, 

 into as many segments, which recall, in a measure, the muscle- 

 fiber and the liver-cell or, at least, features characteristic of 

 both these structures. If the blood-plasma can penetrate the 



Tappeiner: Zeitschrift fiir Biologic, Bd. xii, S. 60, 1876. 



