350 



FUNCTIONS OF THE NERVOUS SYSTEM. 



Oblongata. When this is the case, it is observed that the whole mass is not 

 a miniature (so to speak) of the large Cerebellum of Man, but that the central 

 portion (termed the vermiform process) is the part most developed; the lobes 

 not presenting themselves until the organ has acquired an increased dimension. 

 The following table, constructed from materials contained in M. Serres' most 

 valuable Comparative Anatomy of the Brain, will afford some idea of the ma- 

 terials for speculating on the nature of the function of the Cerebellum, which 

 we obtain from this source. The first column gives the diameter of the Spinal 

 Cord, at the second cervical vertebra ; in the two succeeding columns are 

 stated the transverse and the antero-posterior diameters of the Cerebellum ; 

 these dimensions are stated in hundred-thousandths of a metre. The fourth 

 column expresses, in round numbers, the proportion which the diameters of 

 the Cerebellum bear to that of the Spinal Cord ; the latter being reckoned as 1. 



458. This table affords us much scope for interesting speculation, and may 

 be applied to the correction of hypotheses erected upon other foundations. 

 Before we proceed to these, however, a few general remarks may be made 

 upon it. In the first place, the proportional development of the Cerebellum 

 is seen to be smallest in the Vermiform Fishes, which approach most nearly 

 to the Invertebrata; but it is much greater -in the higher Fishes than it is in 

 Reptiles. If we consider in what particular, that may be reasonably supposed 

 to have a connection with this organ, the former surpass the latter, we should 

 at once be struck with their superiority in activity and variety of movement. 

 Passing on to Birds, we remark that the average dimensions of the Cerebel- 

 lum greatly surpass those of the organ in Reptiles ; but that they do not exceed 

 those occasionally met with in Fishes. The greatest size is not found in those 



