440 SPECIAL HISTOLOGY. 



inconsiderable numbers, and running, in part, obliquely ; but of 

 their origin nothing satisfactory could be ascertained. Whether 

 there are still other, and what traces of fibres, the future 

 must show. 



The more intimate structure of the grey substance of the 

 convolutions, is tolerably manifest (vid. 'Mikroskop. Anatomie/ 

 PI. IV, fig. 2). It is most conveniently divided into three 

 layers, an external, white; a middle, 'pure grey; and an 

 internal, yelloivish red. The latter, in thickness almost equal 

 to the other two, usually presents, on its outermost border, a 

 clear, frequently white streak, and occasionally, more inter- 

 nally, a second, thinner and less white layer, so that there 

 are in fact four or even six successive laminae: I. a yellowish- 

 red layer (iuner part); 2. the first white streak ; 3. yellowish-red 

 layer (outer part) ; 4. second white streak; 5. the grey layer; 

 6. superficial white layer. The grey substance contains, in its 

 whole thickness, both nerve-cells and nerve-fibres ; and besides 

 these, much granular matrix-substance, exactly like that of the 

 cerebellum. The nerve- cells are not easily investigated, except 

 in preparations in chromic acid, and in all the three la3^ers they 

 agree in this respect, that by far the greater number of them 

 are furnished with from one to six processes, which give off 

 numerous branches, and ultimately form extremely fine, pale 

 fibrils of about 00004"' in diameter, differing, however, in 

 respect of size, number, &c. In the superficial white layer the 

 cells are few, small (0*004 — 0008'"), with one or two pro- 

 cesses, and scattered in an abundant, finely granular matrix. 

 The middle or pure grey layer, most abounds in cells, which 

 in it, are closely aggregated also in a granular matrix. 

 Their size varies very considerably, some being very small 

 (0'003 — - 005'"), frequently appearing as little more than 

 nuclei, whilst there are many others of larger dimensions, 

 up to 0-01 6'" and 0-02'" (fig. 149). Their figure is pyriform 

 or fusiform, tri- or multangular, also perhaps more rounded, 

 by far the greater number having from one to six processes, 

 usually three, four, or five; and where this is not the case, they 

 may have been torn off in the preparation, since stumps of 

 them may be very readily noticed in the cells, which are 

 altogether very delicate. In the innermost yellowish-red layer, 

 lastly, the cells are again rather more scanty, though still 



