SIMIA SATYRUS, THE ORANG-OUTANG 509 



clDisolatrral to the j^yraniid (Py), sonic ol w I lost' libers arc slill 111 

 process ol decussation ( P\\). The entn"e section has increased in its 

 diameters, largclx chie to the expansion occasioned b\ the increment in the 

 dorsal sensory nuclei, the addition ol the mierior oinary nucleus and the 

 introduction ot decussatin<i libers Irom the nucleus ol Goll. These inti'rnal 

 arcuate libers pass vcntrad to the central >i;ra\ matter (Con) into the 

 median raphe \\ lure the\ undergo decussation, and enter the mesial tillet. 

 The central pray matter (Cen), somewhat irrei!;ularl\ (|uadrilateral in 

 outline, IS [)artially detached Irom connection witii tlu' remainin<z jiray 

 matter by the internal arcuate libers. It has mi<irated dorsad, with the 

 ellect that the dorsomedian st'plum is be<i:innin<i; to expand and cause the 

 dixergcnce ol the opposed surlac(.'s ol the two alar plates. In the center ol 

 the gra\ matter is a small central canal. The dorsal sensory I i elds are occupied 

 b\ the much increased nuck'i ol'Cioll and Burdach ( N G , N B ), to tlu' latter 

 ol which are appended scattered nuclear masses lormin<j; the nucleus 

 of Blumenau. The relatixi' proportions of the nuclei of Goll and Burdach 

 are cleari\ indicated by the dorsal paramedian sulcus. The substantia 

 gelatinosa trigemini (NR) occupies its usual position lateral to the nucleus 

 of Burdach. It is of considerable size and accompanied by a large descend- 

 ing trigeminal tract ( Trd ). X'cnlral to the substantia gelatinosa is the gray 

 matter constituting the griseal portion ol the reticular lormation ( Rel ). Its 

 indefinite and diffuse character is cons|:)icuous at this le\ei. \ his |)ortion of 

 the ci'iitral axis in the orang contains much ol this ill-deliiietl dilterentiation 

 which is more characteristic of the lower and intermediate primates than it 

 is of the great anthropoids. 



The ventromcsial area ol tiie cross section is occupied by the pyramid 

 ( Py), some libers of which art' still undergoing decussation in a position 

 xentral to the accLimulating libers forming tlie mesial lillct. Lateral to the 



