592 



MANUAL OF HISTOLOGY. 



two are often exactly opposite one another. As a rule the latter are only 

 visible for a very short distance from their point of origin. 



Two species of these elements are recognised by Schulze. In the first 

 place, smaller ones of O0067 mm. in diameter, and smooth edged, which, 

 on treatment with bichromate of potash, acquire great brilliancy of out- 

 line, and are seen to possess one or 

 two small nucleoli and the filaments 

 just mentioned; in the second place, 

 larger elements, 0'0090 mm. in dia- 

 meter, which have distinct nucleoli. 

 These show no polar filaments, but 

 have frequently attached to them 

 small shreds of the fibrous sustenta- 

 cular substance, to which latter they 

 probably belong, while the first 

 form of cell is, by this observer, set 

 down as nervous, and analogous to 

 the granules of the retina. 



There is, however, great differ- 

 ence of opinion upon this point ; 

 and some very weighty authorities, 

 among whom Koelliker, Stieda, and 

 Deiters may be mentioned, look 

 upon the whole as part of the spongy 

 tissue of the sustentacular substance, 

 and deny any connection with nerve- 

 fibres ascending from below. This 

 view we ourselves also are inclined 

 to regard as the most correct. 



A set of small ganglion cells has 

 been described by Koelliker and 

 Schulze as occurring at the border 

 of this stratum, which give off a 

 a number of ramifying processes ; 

 and Meinert speaks of a layer of 

 tangentially coursing nerve fibres, 

 with similarly arranged fusiform 

 cells here. We have already al- 

 luded to this above. 



Turning now to the most external 

 of these two cortical strata, the grey 

 or cellular layer, as it is called, we 

 find its most striking elements to be 

 large ganglion cells (fig. 560), dis- 

 covered many years ago by Purkinje. 

 They lie chiefly in the inner portion 

 of the stratum, but are by no means abundant (fig. 561), and form but a 

 single row. Internally they give off one process only of a different appear- 

 ance from themselves (fig. 560, b). According to Gerlach this breaks up 

 into the fine network of the rusty-brown layer, already alluded to, with its 

 interpolated nuclei, which would be a very peculiar arrangement of the 

 nervous fibres. But although others have expressed their concurrence in 

 this view of Gerlach' s (Hess, RutUowslnj], it must, nevertheless, be declared 



Fig. 560. A ganglion cell of Purkinje, from the 

 human cerebellum, a. cell; 6, pointed pro- 

 cess; c, anller-like ramifications, with delicate 

 branches, /; d, axis cylinder; e, nerve fibre 

 (d and e, completed from the dog). 



