1863.] 721 



branches which form part of the intervening network, as I have 

 described on former occasions. The opposite end of each pyramidal 

 cell tapers gradually into a straight process which runs directly 

 towards the surface of the convolution, and may be traced to a sur- 

 prising distance, giving off minute branches in its course, and be- 

 coming lost in the surrounding network. Many of these cells, as 

 well as those of a triangular, oval, and pyriform shape, are as large 

 as those of the anterior grey substance of the spinal cord. 



In other convolutions I again found the vesicular structure some- 

 what modified. Tn the surface convolution, for instance, at the side 

 of the longitudinal fissure, on a level with the anterior extremity 

 of the corpus callosum, all the three inner laminae are thronged with 

 pyramidal, triangular, and oval cells, of considerable size, and in 

 much greater number than in the situation last mentioned. Between 

 these, as usual, is a multitude of the smaller cells. 



The cells of the convolutions in man certainly differ in some respects 

 from those of the larger mammalia from those, for instance, of the 

 ox, sheep, and cat. 



In the early foetal brain of mammalia and man the structure consists 

 of one uninterrupted nucleated network. As development advances, 

 separate layers may be distinguished. In a foetal sheep 2| inches 

 long, for instance, I distinguished six layers in a transverse section 

 of the brain, extending from the vertex to the interior of the lateral 

 ventricle. The first, second, and third corresponded to those which 

 I have described in the convolutions of the adult human brain, and 

 still consisted of roundish nuclei connected by a network of fibres. 

 The third of these layers consisted chiefly of a dark and dense 

 stratum of nuclei, exactly similar to that which the caput cornu 

 posterioris of the spinal cord presents at the same period of develop- 

 ment. The fourth layer consisted chiefly of elongated and radiating 

 groups of nuclei. The fifth layer was dark, containing nuclei and 

 a dense stratum of transverse fibres. The sixth layer was com- 

 posed of epithelium, uninterruptedly connected with the network of 

 the preceding layers, and having precisely the same appearance as 

 the epithelium of the cord at the same period of development. 



On the Structure of the Cerebellum. The observations of Gerlach 

 on the minute structure of the cerebellum are in the main confirmed 

 by my own. I must state, however, that the outer grey layer con- 



