CHEMISTRY OF NERVOUS MATTER. 53 1 



368, II), e.g., in the spinal ganglia. The soft body of the cell, which is provided with several 

 processes, is covered by a thick, tough capsule composed of several layers of connective-tissue 

 corpuscles ; while the inner surface of the composite capsule is lined by a layer of delicate 

 endothelial cells (fig. 376). The body of the cells in the spinal ganglia is traversed by a net- 

 work of fine fibrils (Flemming). The capsule is continuous with the sheath of the nerve-fibre. 



Rawitz and G. Retzius find that the cells of the spinal ganglia are tinipolar, the outgoing 

 fibre taking a half-turn within the capsule before it leaves the cell (fig. 376). Retzius [and 

 Ranvier] observed the process to divide like a T. Perhaps this division corresponds to the 

 two processes of a bipolar cell. The jugular ganglion and plexus gangliiformis vagi in man 

 contain only unipolar cells, so that, in this respect, they may be compared to spinal ganglia. 

 The same is the case in the Gasserian ganglion ; while the ciliary, spheno-palatine, otic, and 

 submaxillary ganglia structurally resemble the ganglia of the sympathetic. 



4. Ganglionic cells with spiral fibres occur chiefly in the abdominal sympathetic of the frog 

 (Beetle, J. Arnold). The body of the cell is usually pyriform in shape, and from it proceeds a 

 straight unbranched process (fig. 368, III, n), which ultimately becomes the axis-cylinder of a 

 nerve. A spiral fibre springs from the cell (? a network), emerges from it, and curves in a 

 spiral direction round the former (o). The whole cell is surrounded by a nucleated capsule (m). 

 We know nothing of the significance of the different fibres. 



322. CHEMICAL AND MECHANICAL PROPERTIES OF NERVOUS 

 SUBSTANCE. 1. Proteids. Albumin occurs chiefly in the axis-cylinder and in 

 the substance of the ganglionic cells. Some of this proteid substance presents 

 characters not unlike those of myosin ( 293). Dilute solution of common salt 

 extracts a proteid from nervous matter, which is precipitated by the addition of 

 much water and also by a concentrated solution of common salt (Petroivsky). 

 Potash-albumin and a globulin-like substance are also present. Nuclein occurs 

 especially in the grey matter ( 250, 2), while neuro-keratin, a body containing 

 much sulphur and closely related to keratin, occurs in the corneous sheath of nerve- 

 fibres (p. 528). If grey nervous matter be subjected to artificial digestion with 

 trypsin, both of these substances remain undigested (Kiihne and Eivald). Pure 

 neuro-keratin is obtained by treating the residue with caustic potash. The sheath 

 of Schwann does not yield gelatin, but a substance closely related to elastin 

 ( 250, 6), from which it differs, however, in being more soluble in alkalies. The 

 connective-tissue of nerves yields gelatin. 



2. Fats and other allied substances soluble in ether, more especially in the white 

 matter : (a) Cerebrin, free from phosphorus ( 250, 3). 



Cerebrin is a white powder composed of spherical granules soluble in hot alcohol and ether, 

 but insoluble in cold water. It is decomposed at 80 C, and its solutions are neutral. When 

 boiled for a long time with acids, it splits up into a left-rotatory body like sugar, and another 

 unknown product. Preparation. Rub up the brain into a thin fluid with baryta water. 

 Extract the separated coagulum with boiling alcohol. The extract is frequently treated with 

 cold ether to remove the cholesterin ( W. Mutter). Parkus separated from cerebrin its 

 homologue, homocerebrin, which is slightly more soluble in alcohol, and the clyster-like body, 

 encephalin, which is soluble in hot water. 



(b) Lecithin and its decomposition-products glycero-phosphoric acid and oleo- 

 phosphoric acid ( 251). 



Neurin (or Cholin = C 5 H I5 N0. 2 ) is a strongly alakaline, colourless fluid, forming crystalline 

 salts with acids. It is soluble in water and alcohol, and has been formed synthetically from 

 glycol and trimethylamin. Lecithin is a salt of the base neurin. 



(c) Protagon, which contains N and P, is similar to cerebrin, and is, according 

 to its discoverer, the chief constituent of the brain (Liebreich). 



According to Hoppe-Seyler and Diaconow, it is a mixture of lecithin and cerebrin. [The 

 investigations of Gamgee and Blankenhorn have shown, however, that protagon is a definite 

 chemical body. They find that, instead of being unstable, it is a very stable body.] It is a 

 glycoside, and crystalline, and can be extracted from the brain by warm alcohol, and when 

 boiled with baryta yields the decomposition-products of lecithin. 



3. The following substances are extracted by water : Xanthin and hypoxanthin (Scherer), 

 kreatin (Lerch), inosit ( W. Mutter), ordinary lactic acid (Gscheicllen), acetic and formic acids, 

 uric acid (?), and volatile fatty acids ; leucin (in disease), urea (in uraemia), and a substance 

 like starch in the human brain (Jaffe). All these substances are for the most part products of 

 the regressive metabolism of the tissues'. 



