8o2 MAN 



seems to retain man\ of the cliaractcristics ol tlie \c'ntra! horn in the 

 spinal eord, and were it not lor its detaehnient b\- tln' erossing p\ramidal 

 libers, the general appearanee of the seetion in this respeet would eorrespond 

 closely to that of the upper eer\ ical region of the eord. The eentral gray 

 matter is somewhat broader and more massive than in the lower levels 

 of the axis. It eontains near its eenter the eentral eanal. It has not 

 manifested as yet any of its tendency toward dorsal migration in preparation 

 for the opening of the fourth ^•entriele. Dorsolaterally it is connected bj' a 

 slenck'r cervix with a dorsal gray column, surrounding the periphery of which 

 is the substantia gelatinosa (NR). This substance has much increased in 

 size and has moved into a more lateral position as compared with its con- 

 ditions in the spinal cord. It is beginning to occupy the position \\ hich gives 

 rise at higher levels to the eminentia trigemini. 



The dorsal sensory field exhibits the wide expanse lying between the 

 two laterall\' denected masses of the substantia gelatinosa. The most strik- 

 ing featurt' in it, however, is the proportion of the mesial column of Goli 

 (CG) to the more lati'ral column of Burdach (CB). These two fasciculi 

 of densely m\clini/cd libers arc separated from each other b\- a well- 

 dclined dorsal paramedian sulcus. There is thus no diHicultx' in distin- 

 guishing the lioundaries of the area representing the sensorx inllux Irom the 

 leg and foot and of that serxing in a similar capacity- for tlu' arm and hand. 

 The columnar representati\e of the lower extremity, the coKimn ol Goll, 

 is about one-third the size of the similar represcntatixc of the upper extremity 

 and hand, the column of Burdach. None of the primates shows with such 

 decisiveness the delimitation between these two columns, nor is there any 

 case in which tlu' disparit\' in size between tlu'in is more marked than in 

 man. This dilference denotes a marked incri'ase in the lunctioiial impor- 

 tance of those sensory allerents connected w ith the upper extremity and hand. 

 It is by no means imjilied that the morphological dilferentiation in the hand 



