1 70 



THE LOWER PRIMATES 



with afferent conduction. These nuclei are especially related to a type of con- 

 duction which has to do with the maintenance of equihbriuin. They receive 

 impulses from the receptive organs of the semicircular canals, utricle and 



FIG. 83. MARMOSET. LEVEL OF THE \'ESTIBULAR NUCLEI AND 

 TUBERCULUM ACUSTICUM. 



CTT, Central Tegmental Tract; dt, Deiterso-spinal Tract; cow, Ventral Spinocerebellar Tract; icp, Inferior 

 Cerebellar Peduncle; lo. Inferior Olive; mf. Mesial Fillet; nd, Deiters' Nucleus; nr, Nucleus of Rolando; 

 NSC, Nucleus of Schwalbe; n8. Auditory Nerve; pd, Predorsal Bundle; pl, Posterior Longitudinal Fasciculus; 

 FY, Pyramid; ref, Reticular Formation; rst, Rubrospinal Tract; spt. Spinothalamic Tract; trd. Descending 

 Trigeminal Tract; tub, Tuberculum Acusticum. [Accession No. 146. Section 67. Actual Size 10X4 mm.] 



saccule. The two nuclei which have thus replaced the columns t)f Goll and 

 Burdach are the nucleus triangularis of Schwalbe ( NSc) and the nucleus 

 magnoccllularis of Deiters (ND). The size of these nuclei and their fiber 

 connections with the vestibular mechanism indicates a high degree of organi- 

 zation in the reflex acts connected with balancing. These vestibular nuclei 

 are outstanding features in the section. In their general dimensions they cor- 

 respond with the similar structures of lemur, a fact which would seem to 

 justify the inlerence that the marmosets are as well equipped in balancing 



