NEUROLOGY 293 



them. The central canal is located in the center of the cord. As 

 the cord nears the medulla oblongata the form of the gray matter 

 changes. The second, the third, and the fifth ganglion centers"are 

 arranged laterally, and show a distinct side-horn group. The 

 central canal separates the two Clark's columns; later the side-horn 

 group enlarges and extends ventrally around the anterior horn group 

 and joins on the other side in half-moon shaped formation. 



The central ganglionic mass of the spinal cord, the center for the 

 enteric visceral system, is divided into three complex parts. First, 

 there are cell groups on both sides of the posterior raphe. Second, 

 the half -moon shaped ventral groups extending parallel peripherally 

 described above. Third, lying between groups one and two a com- 

 plex group, which possesses a large collection of cells. These fur- 

 nish splanchnic nerve centers, the anterior supplying motor nerves 

 and carrying motor impulses outward, and the superior sensory 

 which carry impulses to the centers. The cell group of the superior 

 horns takes a sidewise peripheral position (Gadow). 



The cerebellum (Fig. 62, C, 2) is located above the medulla oblon- 

 gata and posterior to the cerebrum. The cerebellum consists prin- 

 cipally of a median lobe called the worm. The lateral lobes are 

 conical and rudimentary. The under part of the worm forms the 

 roof of the fourth ventricle. 



On the upper surface of the cerebellum are numerous transverse 

 markings (in the hen 13 or 14) which divide the lobe into leaves. 

 When the cerebellum is cut lengthwise there is observed on the 

 sectioned surface the peculiar arrangement of the white and the 

 gray matter, the arbor vitae, mentioned above. There is a small 

 cavity in the cerebellum which communicates with the fourth 

 ventricle. 



The cerebellar cortex shows four parts, namely: First, the central 

 part composed of white medullated fibers, between which are 

 arranged neuroglear cells. Second, a rather reddish layer of cells 

 of different sizes. These cells are embedded in a fine ground 

 substance and are about 0.003 mm - m diameter. Third, a plain 

 layer of large pear-shaped ganglion cells, the cells of Purkinje. 

 Fine branches extend outward from the apex of these cells. Fourth, 

 an outer gray layer which consists of small multipolar nerve cells 

 with some neuroglear cells. The color of these three layers, accord- 

 ing to Gadow, depends upon the color of the plumage; that is, if 

 the plumage is dark, this layer is dark; if light, the layers are 



