426 Chemical Differentiation of the Brain 



Moist Brain Tissue: Add alcohol and extract alternately with alcohol and 



ether.* 



Organic extractives in Fraction 2 and 3 are equal to total organic ex- 

 tractives. 



Inorganic constituents in Fraction 2 and 3 are equal to total inorganic 

 constituents. 



Fraction 1 and 2 are soluble in alcohol (85-95 per cent). 



Fraction 3 is insoluble in alcohol; soluble in hot water. 



Fraction 4 is insoluble in alcohol and hot water. 



For a clearer understanding of the terms used in this series 

 of papers, the following interpretation of the chemical nature, 

 anatomical distribution, and physiological significance of the sub- 

 stances determined, with special reference to the nervous system 

 based both on the studies already made and those presented in 

 this paper, is given below. 



Proteins. 



Chemistry. These represent complex combinations of ammo-acids ren- 

 dered insoluble in water by coagulation with hot alcohol. This fraction 

 has been exhaustively extracted with hot alcohol and should retain only 

 traces of lipoids and fats. The nucleoproteins and the neurokeratin are 

 included in this fraction. 



Anatomical distribution. In the part of the nervous system rich in cells 

 (cortex) the proportion of the proteins is larger than in the white matter. 

 Some of the nucleoproteins are supposed to be associated with the chro- 

 matin and Nissl substance of the nerve cell. The remainder of the nucleo- 

 proteins are represented by the nuclei of the glia cells scattered through- 



3 Although ether is used in the extraction following the first alcohol, it 

 does not remove any considerable amount of material and need not be con- 

 sidered in the above scheme. 



