614 LECTURE XXVI. 



A number of other products containing nitrogen, and, for the most part, 

 phosphorus as well, have been isolated from the brain and described under 

 different names. We have no means of deciding at present anything 

 regarding the nature of these substances as to whether they are simple 

 substance or mixtures, and for that reason will not stop even to enumerate 

 them. 1 



Nervous tissue always contains cholesterol, fat, and albumin, and, in 

 fact, besides nucleoproteids and nucleoalbumins, globulin and albumin. 

 The framework of the tissue is formed by neurokeratin. 



If we compare the amounts of the separate constituents present in 100 

 grams of organic dry substance, we note especially the high albumin con- 

 tent of the nervous tissue. Thus Chevalier 2 analyzed the sciatic nerve of 

 man (the central organs have a similar composition), and obtained the 

 following values: 



Protein 36 . 8 per cent 



Lecithin . . . . . . . 33 . 57 per cent 



Cholesterol 12.22 per cent 



Cerebrin 1 1 . 30 per cent 



Neurokeratin . 3 . 07 per cent 



Other organic substances 4 . per cent 



It is a striking fact that gray brain matter contains much more 

 water than white brain matter. The former contains about 77 per 

 cent of water, while the latter has but 70 per cent. The proteins occur 

 chiefly in the gray matter, and amount to more than one-half of its dry 

 substance. 



The metabolism of nervous tissue is almost entirely unknown to us. 

 Whereas in the case of muscles we are able to detect purely external 

 changes (shortening) during their activity, and at the same time can detect 

 the liberation of heat and consumption of glycogen, this is impossible in 

 the case of nervous tissue. In the ganglion cells alone have histological 

 pictures been described which apparently indicate changes. The nature 

 of these changes is, however, very obscure. We merely know that nervous 



1 As regards the chemical constituents of brain, see J. L. W. Thudichum: Die chem- 

 ische Konstitution des Gehirns des Menschen und der Tiere. Tubingen, 1901. Although 

 the investigations of Thudichum are in certain respects valuable as a basis for further 

 physiological-chemical investigation, still it must be said that none of the many com- 

 pounds described by him was proved to be a simple substance, nor was there given any 

 proof concerning the chemical combination of the substance. There is an almost 

 unexplored field for investigation here. The article by W. B. Halliburton, Die Bio- 

 chemie der peripheren Nerven. Ergeb. Physiol. (Asher and Spiro) Jg. 4, p. 23 

 (1905), is a valuable summary of the work that has been done. 



2 Z. physiol. Chem. 10, 97 (1886). 



