QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE, 191 
processes, which break up into still smaller ones. One of the 
principal processes is at its commencement thick and tapers 
off in its course to the surface of the cortex, giving off at the 
same time, lateral twigs. The other process is, on the contrary, 
thin at its commencement, starts from the nucleus and passes 
direct into the axis-cylinder, which after a short course 
enlarges and becomes invested with a white sheath, and is 
therefore undoubtedly continued in the form of a nerve. 
These giant-cells are chiefly situated in the fourth cortical 
layer, but not in a continuous sheet, forming on the other 
hand, groups of one, two, three, or more, which are ‘3 to 
“7 m.m. distant from one another. These groups are found 
more sparingly in the brains of quite young individuals, and 
in old persons the cells have a peculiar yellow nucleus, not 
tinted by carmine. ‘They are more numerous in the right 
hemisphere than in the left. The white substance in the 
same regions contains an unusual number of thick white 
axis-cylinders, which in their arrangement and_ thickness 
resemble the axis-cylinders of the anterior cornua of the 
spinal cord. 
These cells are found in the corresponding situations in 
every human brain, as well as in various apes. In the: dog 
they are somewhat smaller, but still the largest in the nerve- 
centres. ‘They are found in this animal only in the lobe 
bordering the sewlews cruciatus, which has become known 
through the physiological researches of Fritsche and Hitzig ; 
and in the convolution adjacent to this lobe. In man and the 
higher apes, they are found in a lobe not clearly recognised by 
anatomists which Betz calls lobulus paracentralis, being 
found on the inner side and in front of the fissure of Rolando, 
on the inner surface of the hemisphere. It is separated in 
front by a fissure from the first frontal convolution; behind 
by a fissure from the lobulus quadratus, and is bounded 
below by the gyrus fornicatus. This lobe Betz believes to be 
identical with that described above from the dog, though 
the latter is situated on the outer and anterior surface. In 
both cases he believes it to constitute a “ motor centre.” 
The posterior centre is larger than that just described, but 
varies in size, according to the development of the external 
occipital fissure and the transitional convolutions. It is 
distinguished by the presence of large cells (already described 
by Meynert) which have few protoplasmic processes. Those 
of the processes which run towards the internal surface, 
never reach it, but take a horizontal course and effect a com- 
munication of the cells with one another. The processes 
which run in the opposite direction are less considerable, 
