CHEMICAL CHANGES IN HUMAN BRAIN 453 



Sulphatids 



Because of uncertainty concerning the sulphatids found in the 

 brain, the report for this constituent is open to question. It is 

 assumed, however, that it is a cerebroside and phosphatid fastened 

 together by a sulphate radicle (Koch, '10). The sulphatids are 

 very closely related to the cerebrosides in physiological function 

 and anatomical distribution. The sulphatids seem to be more 

 fundamentally necessary because they are found earlier (table 

 10). They may be related to conductivity in axis cylinders. 

 Small amounts are present in very early fetal life (tables 1, 4, and 

 6). Soon after birth the amounts formed are greatest (table 12), 

 but there is no time during life when this compound is not being 

 produced. Probably it is concerned in the rivalry between 

 structure and function, helping the former to victory in stability 

 of activity, and finally in death. This is one of those substances 

 so necessary for highly specialized brain work, but so detrimental 

 to continued growth. 



Proteins 



The most important protein of the brain, because of its greater 

 lability, is probably nucleoprotein a (McGregor, '17). One 

 would expect it to be associated with the vital functions. It 

 probably is a combination of the globulin a, globulin b, and the 

 nucleoprotein of an earlier worker (Halliburton, '94). Nucleo- 

 protein b is mUch more stable and may be the protein of the 

 chromatin and Nissl bodies, thus related to the hereditary quality 

 of the nerve cell. Neurokeratin is stable and probably is con- 

 nected with the structure of the nerve sheaths. It is highly im- 

 portant to know how these different proteins increase with growth, 

 but we have only indirect evidence of what these changes are. 

 From the data on total protein, protein phosphorus and protein 

 sulphur (table 11), we can get an idea, of what is happening, 

 however, Thus indirectly we can suggest that neurokeratin ap- 

 proaches a maximum percentage at two years of age, but is 

 present in very small amounts in even early fetal life. Nucleo- 

 protein b is probably present in largest percentage amounts in 



