42 



THE LOWER PRIMATES 



The pyramidal bundles forming this decnssation arc relatively narrow, 

 in this respect bearing out the impression gained from the surface relief of 

 the pyramid which indicates a limited capacity for volitional control over 



FIG. 22. LEMUR MONGOZ. LEVEL OF THE PYRAMIDAL DECUSSATION. 



CB, Column of Burdach; cen. Central Gray Matter; CG, Column of Goll; dt, Deiterso-spinal Tract; fle. 

 Dorsal Spinocerebellar Tract; cow, Ventral Spinocerebellar Tract; nr, Nucleus of Rolando; pv. Pyramidal 

 Tract, Pyramidal Fibers; pvx. Pyramidal Decussation; ref, Reticular Formation; rst. Rubrospinal Tract; 

 SPT, Spinothalamic Tract; trd. Descending Trigeminal Tract; ven, Ventral Gray Matter. [Accession No. 

 147.* Section 57. Actual Size, 9X5 mm. In all actual measurements fractions of the millimeter have been 

 disregarded.] 



the animal's voluntary muscles. As a corollary it may be inferred that the 

 small pyramidal system bespeaks a small ability on the part of the animal 

 to acquire learned reactions. From observation of lemurs in captivity, 

 it is apparent that they learn little more, either by imitation or repetition, 

 than in the free state. 



*The numbers mentioned at the end of each caption in this and the following cross 

 sections refer to the Study Collection of the Columbia University Neurological Department. 





