370 THE INTERMEDIATE PRIMATES 



tached from this nucleus and lying near the periphery is an equally large 

 sensory element, the nucleus oi Blumenau (NBI). In a position ventral 

 to the nucleus oi" Blumenau is the substantia gelatinosa trigemini (NR), 

 in contact externally with the fibers of the descending trigeminal tract 

 (Trd). It is now possible to compare with more critical sense the relative 

 dimensions of the three major elements entering into the dorsal sensory 

 field, and representing the dermatomic areas of the body from the soles of 

 the feet to the crown oi the head. These elements serve all modalities of dis- 

 criminative sensibility within the same limits. It is apparent that the column 

 and nucleus of Burdach i'ar exceed in size either of their neighboring 

 structures, the nucleus of Goll (NG) situated mesial to them, or the 

 substantia gelatinosa trigemini (N R) situated ventral to them. On the 

 strength of this comparison, the conclusion seems tenable that the hand and 

 upper extremity have gained much in prominence as sensory organs over the 

 head and face, w hich latter are only mcagerly represented bj'' the relatively 

 small receiving station of the trigeminal nerve. Quite as much do the lower 

 extremity and tail suifer by the comparison as sensory organs. In Macacus 

 rhesus the tail is short and has developed none of that prehensile speciali- 

 zation which characterizes the new-world monkeys. 



Passing through the substantia gelatinosa trigemini (NR) are a few 

 emergent fibers of the eleventh nerve, making their way toward the periph- 

 ery of the axis. The fibers of the twelfth nerve are also seen taking origin in 

 the ventral portion of the central gray matter (Cen ) and passing forward 

 in the direction of the inierior olivary nucleus ( 10 ). The reticular formation 

 ( Ref ) occupies a central position, and through it pass a number of internal 

 arcuate fibers from the nucleus of Burdach, while large masses of decussating 

 fibers extend inward iVom origins in the nucleus of Goll and pass mesially to 

 enter the decussation of the mesial iillet ( Mf ). The collected bundle of the 

 pyramid (Py) occupies its usual ventromesial position and afiords a clear 



