178 THE BRAIN OF THE TIGER SALAMANDER 



perior sensory V nucleus terminating in the cerebellum and the neu- 

 ropil of the V nucleus of the opposite side (figs. 31, 32, 91). The latter 

 is a true trigeminal commissure. 



The com. vestibulo-lateralis cerebelli is a more dispersed collection 

 of unmyelinated and lightly myelinated fibers assembled from the 

 auricles (figs. 31 36, 91). Included among them are root fibers of the 

 vestibular nerve {comxb.VIII) and secondary fibers of the lateral- 

 line system of nerves {com.cb.l.L). These are mingled at their crossing 

 in the cerebellar alba. Whether any primary root fibers of the lateral- 

 line nerves decussate in this commissure is not clear in our material ; 

 apparently they do not. 



PROPRIOCEPTIVE FUNCTIONS OF THE CEREBELLUM 



In the initial differentiation of the cerebellum and in its normal 

 functions in all animals, proprioception has played a dominant part. 

 Nevertheless, it must be recognized that all sensory systems may 

 participate in cerebellar control of muscular movements (Larsell, 

 '45), a control that is applied to the motor adjustors as going con- 

 cerns at every phase of their operations. The significance of the cere- 

 bellum as "the head ganglion of the proprioceptive system" (Sher- 

 rington) is discussed in chapter x in connection with a critique of the 

 proprioceptive system as a whole. 



