CHAPTER X. 

 BRAIN AND NERVES. 



ON account of the difficulty of making a mechanical separation 

 and isolation of the different tissue elements of the nervous central 

 organ and the nerves, we must resort to a few micro- chemical re- 

 actions, chiefly to qualitative and quantitative investigations of the 

 different parts of the brain, in order to study the different chemical 

 composition of the cells and the nerve-tubes. The chemical investi- 

 gation of this part is accompanied with the greatest difficulty; and 

 although our knowledge of the chemical composition of the brain 

 and nerves has been somewhat extended by the investigations 

 of modern times, still we must admit that this chapter is yet to-day 

 one of the most obscure and complicated in physiological chemistry. 



Albuminous bodies of different kinds have been shown to be 

 chemical constituents of the brain and nerves. A part of these are 

 insoluble in water and dilute neutral-salt solutions, and part are 

 soluble therein. Among the latter we find albumin and globulin. 

 Nudeoalbumin, which is often considered as an alkali albnminate, 

 also occurs. It seems unquestionable that the albuminous bodies 

 belong chiefly to the gray substance of the brain and to the axis- 

 cylinders. The same remarks apply to nuclein which v. JAKSCH 

 found in large quantities in the nerve subtances. Neurokeratin 

 (see page 35), which was first detected by KiJHNE,and which partly 

 forms the neuroglia, and which as a double sheath envelops the 

 outside of the nerve medulla under SCHWANN'S sheath and the 

 inner axis-cylinders, chiefly occurs in the white substance (KuHJjE 

 and CHITTENDEN, BAUMSTARK). 



The phosphorized substance protagon must be considered as one 

 of the chief constituents, perhaps the only constituent (BAUM- 

 STARK), of the white substance. This last-mentioned substance 



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