n6 THE CHEMISTRY OF THE TISSUES AND ORGANS. 



Solids. The solids may be divided into the following classes : 



(a) Proteids. These comprise a very considerable percentage of the 

 solids, especially in the grey matter (over 50 per cent.). 



(b) Neurokeratin and nuclein. 



(c) Phosphorised constituents ; especially protagon and lecithin. 



(d) Cerebrins. Nitrogenous substances of unknown constitution. 



(e) Cholesterin. Especially abundant in white matter. 



(/) Extractives. Creatine, 1 xanthine, 2 hypoxanthine, 2 inosite, 3 lactic 

 acid, 3 leucine, 3 uric acid, 3 and urea. 



(g) Gelatin and Fat. From the adherent connective tissue. 



(A) Inorganic salts. The total mineral matter varies according to 

 different writers from 01 to 1 per cent. 



Geoghegan 4 gives the following figures in parts per thousand of 

 brain : 



Total ash 



Potassium 



Sodium 



Magnesium 



Calcium 



0-4 

 0-9 

 0-2 

 0-1 

 0-01 



to 1-2 

 2-0 

 0-7 

 ,, 0-2 

 0-09 



The grey matter is stated by Schlossberger to be richer in total ash 

 than the white, but poorer in phosphates ; Petrowsky, on the other hand, 

 found more phosphates in grey than in white matter. 



The following table gives some typical quantitative analyses which 

 have been made of the proportion in which the principal solids occur in 

 different nervous structures : 



The quantitative work 1 8 have done on this question may be sum- 



1 Miiller, Ann. d. Chem., Leipzig, Bd. ciii. S. 141 ; Stadeler, Journ. f.prakt. Chem., 

 Leipzig, Bd. Ixxii. S. 256. 



2 Stadeler, Ann. d. Chem., Leipzig, Bd. cxvi. S. 102; Scherer, ibid., Bd. cvii. 

 S. 314. 



3 Miiller, loc. cit. ; see also Strecker, Ann. d. Chem., Leipzig, Bd. cv. S. 316. 



4 Ztschr. f. physiol. Chem., Strassburg, Bd. i. S. 330. 



5 Petrowsky, toe. cit. 



6 Moleschott, loc. cit. 



7 Josephine Chevalier, Ztschr. f. physiol. Clicm., Strassburg, Bd. x. S. 97. 



8 Halliburton, Journ. Physiol., Cambridge and London, 1893, vol. xv. p. 90. 



