NERVES. 357 



spinal cord it is deep seated, forming the central portion 

 of these organs. 



The secreting substance or grey matter of the brain is 

 made up of a granular base, in which are contained numerous 

 nucleated cells of different sizes and forms. In the grey- 

 matter of the convolutions of the brain the granular base 

 is very abundant, the cells small and round, and in less 

 proportion than the base itself: in the tuber cinereum, in the 

 cerebellum, and in the grey matter of the cord, the small 

 granular cells are extremely abundant, and the granular 

 base is diminished in quantity. (See Plate XLV. figs. 2, 3.) 



Now the granular base and the small granular cells con- 

 stitute the principle portion of the substance of the grey 

 matter wherever encountered : in certain localities, however, 

 cells of different forms and of considerable magnitude are met 

 with : these cells have been termed ganglion cells. 



Ganglion Cells. Ganglion cells are encountered in dif- 

 ferent portions of the cerebro-spinal system, as in the locus 

 niger of the crura cerebri, in the grey matter of the arbor 

 vita?, and corpus dentatum of the cerebellum ; in the me- 

 dulla oblongata ; in the spinal cord for its entire length, 

 arid according to Valentin and Purkinje, in all the extent 

 of the cerebral hemispheres, especially in the posterior lobes, 

 and in the grey lamina of the spiral fold of the cornu 

 Ammonis. 



These cells vary greatly both in size and shape ; many of 

 them attain a very considerable diameter, and they are, 

 almost without exception, all provided with caudate pro- 

 longations, which are frequently branched. (See Plate XLIV. 



fig- 4.) 



The ganglioniform cells of the locus niger are for the 

 most part small, and irregularly stelliform in shape : those 

 of the grey matter of the cerebellum are pyriform, the 

 spinous and often branched processes, usually two or three 

 in number, proceeding from their narrow extremities : many 

 of the cells of the medulla oblongata are triangular, the 

 spines arising from the angles, and being much produced, 



