MYCETES SENICULUS 221 



complexity in motion resulting from a greater volitional control of the upper 

 extremities. Not alone is this increment in coordination essential to the 

 newer movements of the hand, but now there is the further need of coordina- 



%i«.- 



FIG. 122. MYCETES SENICULUS. LEVEL OF THE VESTIBULAR NUCLEI. 

 CTT, Central Tegmental Tract; dt, Deiterso-spinal Tract; do, Dorsal Accessory Olive; cow, Ventral Spino- 

 cerebellar Tract; icp, Inferior Cerebellar Peduncle; lo, Inferior Olive; mf, Mesial Fillet; nd, Deiters' Nucleus; 

 NFS, Facial Nucleus; nsc. Nucleus of Sclnvalbe; n8. Auditory Nerve; nr. Nucleus of Rolando; nhy. Nucleus 

 Hypoglossus; pd, Predorsal Bundle; PL, Posterior Longitudinal Fasciculus; py. Pyramid; ref. Reticular 

 Formation; rst. Rubrospinal Tract; spt, Spinotfialamic Tract; trd. Descending Trigeminal Tract; tub, 

 Tuberculum Acusticum; vo. Ventral Accessory Olive. [Accession No. 148. Section 165. Actual Size, 

 13X5 mm.] 



tion arising from the fact that the animal depends more upon the hindhmbs 

 in locomotion than do the lower forms. This requirement appHes hkewise to 

 the partial attainment of the upright posture as well as the animal's tendency 

 to sit upon its haunches and to balance itself in this position. 



All of these factors demand a more extensive development of coordina- 

 tive as well as equihbratory control, and this control in its more remote 

 secondary effects has aided in the development of the hand. 



