270 



THE LOWER PRIMATES 



These coefficients are shown in the accompanying table: 



Coefficients of the Red Niclels in the Lower Primates 



LACK OF STRICT FUNCTIONAL PARALLELISM BETWEEN 

 THE DENTATE NUCLEUS AND THE NUCLEUS RUBER 



One fact, however, is not satisfactorily explained by these data; namely, 

 that the increment of the dentate nucleus in these species does not vary pari 

 passu with the increment of the red nucleus. This disparity probably indi- 

 cates a lack ot strict tunctional parallelism between the dentate nucleus on 

 the one hand and the nucleus ruber on the other. Such disparity may be 

 explained by certain fibers arising in the red nucleus and passing forward 

 through higher levels to the suprasegmental portions of the axis. There is 

 also some evidence to indicate that certain descending fibers from the region 

 of the corpus striatum connect the latter body to subadjacent aggregations 

 of gray matter in the nucleus ruber. This nucleus may, therefore, represent a 

 composite relay station into which enter impulses not only from the cerebel- 

 lum, but certain others from the corpus striatum as well. Thus, insofar as the 

 functional significance of the red nucleus is concerned, variations in the 

 increment of its expansion are perhaps less important as bearing upon 

 the function of coordination than those of the dentate nucleus. It may be 

 regarded, however, as collateral evidence in relation to this function, and is 

 not without value in estimating the progressive changes going forward in the 

 cerebellum. 



