14 Journal of Comparative Neurology. 



fibers. F. Mayer ('97) has mentioned the three pairs of cells 

 in the vicinity of III as giving origin to Mullerian fibers. 



c. General and special cutaneous centers (somatic). 



These centers include the nucleus funiculi, the nucleus 

 trigemini spinalis, the tuberculum acusticum, and the cerebel- 

 lum. It will be necessary to give a somewhat more complete 

 topographical description of these centers and of the nerve 

 roots than was given in the general account above. 



As the cord passes into the medulla there is a very great 

 thickening of the grey matter just lateral to the central canal 

 and gradually cells spread through the dorsal tracts, forming a 

 diffuse nucleus funiculi (Fig. 9). None of these cells invade 

 the most median part of the dorsal tracts which belongs to the 

 fasciculus communis system. Farther forward the region of 

 the dorsal tracts and nucleus funiculi becomes transformed into 

 three distinct structures. There appears first in the peripheral 

 part of the nucleus and parallel with the surface of the medulla, 

 a thin crescent-shaped plate or lamina of cells (Fig. 9), which 

 are evidently derived from the nucleus funiculi but gradually 

 become distinct from it. The body of the nucleus is continued 

 forward by a large tract of fibers, the spinal V. Throughout 

 its whole extent the spinal V has cells scattered among its fibers 

 so that it retains the appearance of the nucleus funiculi, al- 

 though the cells are not so numerous (Fig. i i a). At the same 

 time that the nucleus funiculi merges into the spinal V tract the 

 plate of cells becomes divided into two distinct nuclei (Fig. 9 a). 

 One of these lies directly dorso-lateral to the spinal V and ac- 

 companies this tract throughout nearly its whole extent. In its 

 caudal part it is a compact nucleus with a light space about it. 

 Although its cells decrease in number and become less easily 

 distinguished from the nucleus above it as it passes forward, it 

 is recognized as a light space directly overlying the spinal V 

 and separating it from the VII and VIII roots, and is finally 

 replaced by the collection of spindle cells to be described below. 

 I shall call this the nucleus of the spinal V. 



The other nucleus developed from the common lamina of 

 cells lies just dorsal to the last and in its caudal part appears 



