SUMMARY OF STRUCTURES 257 



III the case of the Rolandie nueleus, although the area of innervation 

 which it represents (the face and ventral portion of the head) is exquisitely 

 axial in its distribution, this sensory territory of the body manifests consider- 

 able iunetional variabiHty according as the animal depends more or less upon 

 the head and face tor the direction of its locomotion. 



A COMPARISON OF THE NUCLEI OF GOLL AND OF BLRDACH 

 IN THE LOWER PRIMATES 



A comparison of the nucleus of Goll in lemur, tarsier, marmoset and 

 mycetes shows an actual increase in size in the howling monkey, accounted 

 for largely by the presence of a well-defined nucleus of Bischotf. In lemur the 

 planimetric coetlicient of the nucleus gracilis (Golf) is 4.1 per cent, in tarsius 

 2.6 per cent, in marmoset, 6.8 per cent, while in mycetes it reaches 13.1 per 

 cent. All of these forms are essentially quadrumanal. Such increase as occurs 

 in the size of the nucleus of Goll in these species cannot be attributed to 

 essential modifications in the hindlimbs which, specialized as they are for 

 arboreal life, become more or less standardized by this fact. They are subject 

 to but little variation. The motive of this nuclear expansion must in conse- 

 quence be sought elsewhere than in the specialization of the feet. The most 

 obvious possibility to suggest itself is the specialization of the tail. In lemur, 

 tarsier and marmoset the planimetric coefficient of the nucleus gracilis shows 

 no striking diflerences. In these animals the tail serves as a balancing and 

 steering organ. It has developed no prehensile qualities and thus has become 

 but little specialized in its sensory capacity-. As might be presumed, such an 

 organ would not exert much influence tending to efl'ect expansion in the 

 sensory receiving nuclei. 



In the case of mycetes, however, the nucleus of Goll shows a marked 

 expansion. Its coefficient exceeds that of marmoset by nearly ~ per cent and 

 that of lemur by 9 per cent. Such a striking advance as this must have more 



