CHEMISTRY OF NERVOUS TISSUE. 75 



Geoghegan gives the following as representing parts per 1000 

 of brain : 



Total ash . . 2.9 to 7.1 , Chlorin . . 0.4 to 1.2 



Potassium 0.6 "1.7 



Sodium 0.4 "1.1 



Magnesium 0.0 " 0.07 



Calcium . 0.005" 0.02 



PO 4 0.9 "2.0 



CO 3 0.2 "0.7 



SO 4 0.1 "0.2 



Fe(POJ, 0.01 " 0.09 



Halliburton gives the following table, which shows the propor- 

 tion of water, solids, and proteids in different portions of the 

 nervous system. The table represents mean analyses of the organs 

 of adult human beings, dogs, cats, and monkeys : 



Percentage of 



Water. Solids. proteids 



in solids. 



Gray matter of cerebrum 83.467 16.533 51 



White " " 69.912 30.088 33 



Cerebellum 79.809 20.191 42 



Spinal cord as a whole 71.641 28.354 31 



Cervical cord 72.529 27.471 31 



Dorsal " 69.755 30.245 28 



Lumbar " 72.639 27.631 33 



Sciatic nerves 61.316 38.684 29 



The percentage of neurokeratin is in gray matter 0.3 ; in white 

 matter, 2.2 to 2.9 ; and in nerve, 0.3 to 0.6. 



Proteids of Nervous Tissue. The proteids are : 1. A globulin, 

 coagulated by heat at 47 C., analogous to the cell-globulin 

 derivable from cellular tissues generally ; 2. Nucleoproteid, which 

 coagulates at 56-60 C. and contains 0.5 per cent, of phosphorus ; 

 and 3. A globulin coagulating at 70-75 C., analogous to a glob- 

 ulin obtained from the liver. 



Protagon. It was for some time undecided whether this sub- 

 stance, which was separated from the brain by Liebreich, was a 

 definite substance or a mechanical mixture of lecithin and cerebrin; 

 but the evidence now at hand seems conclusive in favor of its 

 definiteness of chemic composition. Its percentage composition, 

 as given by Garngee and Blankenhorn is C, 66.39 ; H, 10.69 ; 

 N, 2.39; P, 1.068; and O, 19.462. The empirical formula is 

 C^H^NgPO^. It is probable that there are more than one pro- 

 tagon. 



Cerebrin. This constituent of nervous tissue should be spoken 

 of as cerebrins, as there are more than one. The constitution of 

 them is not known. They contain nitrogen and yield galactose 

 on hydration. They are also called cerebrosides, and are constitu- 

 ents of the medullary sheaths, and are also found in the yolk of 

 egg, pus-corpuscles, and spleen-cells. 



