LEMUR MONGOZ 51 



this important proprioceptive system so highly developed in these tree-Hving 

 animals. 



Situated between the tubereuhini acusticum (Tub) and Deiters' 

 nucleus is the restiform body (ICP) which represents an aggregation of 

 ascending fibers from the spinal cord and oblongata on their way to the cerebel- 

 him. These ascending cerebellar fibers come from several different sources and 

 serve the purpose of conveying to the cerebelhim afferent impulses necessary, 

 as it were, to orient the cerebelhim m its activity of transmitting to the 

 muscles those impulses essential to coordination. An exact adjustment of 

 action exists between the various groups of muscles in the body in order to 

 maintain such coordination. Since the cerebellum is specialized to regulate 

 the factors entering into this function, it naturally follows that the organ 

 must at all times be in possession of information concerning the varying 

 tensional status of all the muscles of the body. Were this not the case it 

 would be impossible for the cerebellum to transmit to the muscles the ten- 

 sional control essential to the execution of ail muscular acts. Thus the sig- 

 nificance of the afferent cerebellar connections as indicated by the restiform 

 body may be clearly discerned. The degree of development of this structure 

 discloses the extent to which the animal is dependent upon its coordinating 

 mechanism. 



LEVEL OF THE CEREBELLAR N'UCLEI (PIG. 2~) 



At the level of the cerebellar nuclei certain structures which fur- 

 nish a criterion concerning the functional capacity of the cerebellum make 

 their appearance for the first time. These are the cerebellar nuclei. Only 

 a portion of the cerebellum is shown in this cross section. Structurally, the 

 organ consists of a central division, the vermis (Ver), and two lateral 

 lobes or hemispheres. The beginning of the lateral lobe is indicated in the 

 cross section. Immediatelv mesial to the mass of medullarv substance 



