626 CHEMISTRY OF NERVOUS TISSUE. 



2. Ganglia with connective-tissue capsules (sheaths of Schwann) (II) occur 

 (about 50 u in diameter) in the peripheral nerve-nodes. The soft cell-body, pos- 

 sessing two or more cell-processes, is surrounded by a firm capsule of cells closely 

 applied to one another. The cell-body of the spinal ganglion cells is traversed 

 by fine fibers ; the capsule is later on connected with that of the nerve-fiber. 



3. Bipolar ganglia are best seen in fish, for example in the spinal ganglia 

 of the ray and the shark, as well as in the Gasserian ganglion of the pike. They 

 appear as nucleated spindle-shaped swellings of the axis-cylinder (on the right, 

 next to I). The nerve-marrow is often absent where the ganglion is interposed 

 in the course of the fiber. Occasionally, however, the marrow, and always the 

 sheath of Schwann, is continued over the ganglion. 



4. Ganglia surrounded with fibers occur in the sympathetic system of the 

 frog. From the pear-shaped cell (III, n) a process that remains non-medullated 

 extends in one direction, and perhaps further on divides into two branches. In ad- 

 dition, on the surface of the cell, a second nerve-fiber is connected with an extremely 

 delicate network of fine fibers. The second nerve-fiber winds around the first 

 in a spiral manner and then proceeds in another direction (o) as a medullated 

 fiber. Both cell and process are enclosed in a nucleated capsule (m) . The straight 

 fiber has been thought to conduct in a cellulifugal direction, the spiral fiber in a 

 cellulipetal direction. It is possible, however, that the spiral fiber is derived 

 from another ganglion-cell. 



The cells in the peripheral ganglia are deserving of special consideration. They 

 may be divided into two kinds: (i) the cells of the sensory ganglia, including 

 the spinal ganglia, and on the cerebral nerves the Gasserian ganglion, the petrosum 

 glosso-pharyngei, the jugular ganglion, and the nodose plexus of the vagus, the 

 auditory ganglion, the geniculate ganglion. From the pear-shaped cells extend 

 short prolongations that become gradually thinner and divide into two processes 

 diverging in the shape of the letter T an d becoming medullated nerve-fibers. 

 Only the ganglia of the auditory nerve have cells with bipolar processes. The pro- 

 cess from the peripheral sensory area to the ganglion is the cellulipetal- dendrite. 

 The neurite of the cell passes, however, in a cellulifugal direction into the cen- 

 tral nervous system (in the case of the spinal ganglia it passes through the 

 posterior roots into the spinal cord) and breaks up in a dendritic manner. 



Every cell of the spinal ganglia has a connective-tissue capsule lined by a 

 single layer of epithelium. The cell-body exhibits a granular chromophilic de- 

 position and always pigment, while the ground-substance of the protoplasm has 

 a reticular structure, and the nucleus is without chromatin. 



2. The second group of peripheral ganglia contains sympathetic ganglion-cells. 

 It includes in the course of the cerebral nerves the sphenopalatine, the otic, sub- 

 maxillary, and ciliary ganglia, and all ganglia in the distribution of the sympa- 

 thetic system. The cells of the sympathetic system have numerous dendrites 

 and a single neurite. The latter becomes a non-medullated nerve-fiber with neu- 

 rilemma, and it leaves the ganglion to surround the nerve-cells of other ganglia 

 with a network or to terminate on a blood-vessel, while the dendrites ramify 

 within the ganglion. The nerve-fibers passing from the central nervous system 

 to the sympathetic ganglia surround the cells with a delicate network. 



Numerous blood-capillaries surround the individual ganglion-cells, which also 

 are provided with large lymph-spaces. 



CHEMISTRY OF NERVOUS TISSUE. 

 MECHANICAL PROPERTIES OF NERVES. 



Proteids. Of the solid constituents of the gray matter about one- 

 half are proteids; of the white matter one-third. There are present 

 two phosphorus-free globulins and a nucleoalbumin (almost absent from 

 the white matter). 



One of the globulins is precipitable by a little neutral salt, and coagulates 

 at 47 C. It is present also in leukocytes, muscles, and the liver. The other 

 globulin is precipitated only on saturation with magnesium sulphate and coagu- 

 lates at 70. It is present also in liver-cells. The nucleoalbumin, containing 0.5 

 phosphorus, coagulates between 55 and 60 and is precipitated from a watery 

 extract of brain-material by acetic acid. 



