41 8 'Journal of Comparative Neurology and Psychology. 



1. Short paths, mostly unmedullated, to the formatio reticu- 

 laris grisea of the same side and similar tracts, partly medullated, 

 to the formatio reticularis of the opposite side through the dorsal 

 commissure (somatic portion of the commissura infima Halleri 

 in the oblongata). The number of these fibers in any region 

 varies in proportion to the size of the somatic sensory centers. 



2. Broad tracts (chiefly medullated) directly to the ventral 

 cornu of the same side and opposite side (through the ventral com- 

 missure). 



3. Long paths of medullated fibers to the formatio reticularis 

 alba of the same and the opposite side (crossing in the ventral com- 

 missure). These are both ascending and descending. 



4. The ventro-lateral funiculus contains large uncrossed de- 

 scending tracts which must be regarded as more highly developed 

 fascicles of the tracts last mentioned (fasciculus bulbo-spinalis). 



5. Likewise derived from the formatio reticularis alba are the 

 heavily medullated internal arcuate fibers which pass from the 

 somatic sensory centers through the ventral commissure to the 

 tractus spino- et bulbo-tectalis (lemniscus). These are chiefly or 

 wholly ascending. 



6. Accompanying the latter are internal arcuate fibers for the 

 ventral funiculi of the opposite side. These are doubtless long 

 descending tracts for spinal cord reflexes. 



7. From the region of the funicular nuclei there is also an 

 uncrossed tract to the cerebellum, tractus spino-cerebellaris. 



8. Commissural fibers, both medullated and unmedullated, 

 in the somatic portion of the commissura infima Halleri from the 

 nuclei of one side to those of the opposite side. 



It appears, then, that the chief tracts for eflPerent impulses from 

 the somatic sensory centers to distant regions are the descending 

 paths in the ventral funiculus (crossed) and the ventro-lateral 

 funiculus (crossed and uncrossed) and the ascending path in the 

 tractus spino-et bulbo-tectalis or lemniscus (wholly crossed) to 

 terminate in the opposite optic lobe. The former is for direct 

 reflex movements of the body as a whole (unspecialized somatic 

 motor type); the latter is for correlation of cutaneous stimuli with 

 visual and other cerebral nerves, especially for the coordination 

 of movement of the eye-muscle nerves (specialized somatic motor 

 type). Throughout the spinal cord there is in addition to the tracts 

 just mentioned a large uncrossed ascending secondary tactile path 



