370 S. HATAI 



liver or kidneys and comes very close to the testes, which gives 

 the highest value. The meaning of the higher non-protein 

 nitrogen value found in the brain, when compared with the total 

 nitrogen in either the liver or kidneys, can not be readily ex- 

 plained, and we merely record the fact as one of interest. We 

 may also note here that the amount of non-protein nitrogen 

 found in the blood is very close to that found in the blood of 

 other mammals (see Bock, '17). 



GRAY AND WHITE MATTER IN THE BRAIN 



Since the central nervous system is composed of the so-called 

 gray and white matter, structures which are widely different 

 from each other, we thought it highly desirable to determine the 

 non-protein nitrogen, as well as the nitrogen of the several organic 

 extractives, in these two structures. For this purpose the sheep's 

 brain was chosen on account of the ease with which fresh material 

 could be obtained. I may here emphasize the fact that although 

 the white matter can be obtained free from nerve cell bodies, 

 the gray matter can not be secured without some admixture of 

 white matter owing to the constant presence of the myelinated 

 nerve fibers within it. We can however obtain sufficiently pure 

 gray matter for the purpose of studying the chemical differences 

 existing between these two fractions. 



The procedure adopted was a simple one. The corpus cal- 

 losum was exposed and removed, then, working from within, by 

 means of a sharp scalpel the white matter was scraped from the 

 gray matter of the cortex at the demarcation line which separates 

 them. The gray matter therefore represents the entire thickness 

 of the cortex. The method, though simple, requires practice in 

 order to separate the two fractions quickly, so as to avoid an evap- 

 oration of water. The results of the analysis are given in table 5. 



As wall be seen from table 5 the percentage of nitrogen to 

 the total solids, and also the other nitrogen values given by 

 various organic extractives per gram of the brain solids, are 

 always higher in the gray than in the white matter. Further- 

 more, the values are practically twice as great in the gray as in 

 the white. This 2 : 1 relation here shown is extremely interest- 



