OF THE CEREBELLUM, AND ITS FUNCTIONS. 729 



the anterior and posterior columns of the Spinal Cord and Medulla Oblongata 

 ( 711); and in addition to these, we find a fasciculus of fibres passing between 

 the Cerebellum and the Corpora Quadrigemina, the "iter a cerebello ad testes." 

 The peduncle of its hemispheres on either side contains a mass of gray matter, 



Fig. 193. 



An under view of the cerebellum, seen from behind. The medulla oblongata, m, having been cut off a 

 short way below the pons. (Reil.) c. Pons Varolii. d. Middle crus of cerebellum, e e. Crura cerebri. i. 

 Notch on posterior border. Jc. Commencement of horizontal fissure. I. Flocculus, or sub-peduncular lobe. 

 m. Medulla oblongata cut through, q to s. The inferior vermiform process, lying in the vallecula. p. Pyramid. 

 r. Uvula, n n. Amygdalae, s. Nodule, or laminated tubercle, x. Posterior velum, partly seen. w. Right and 

 left hemispheres of cerebellum. 3 to 7. Nerves. 33. Motores oculorum. 5. Trigeminal. 6. Abducent nerve. 

 7. Facial and auditory nerves. 



which seems to be a ganglionic centre for the fibres that pass upwards to it from 

 the Spinal Axis. Thus the Cerebellum has no direct connection with the Cere- 

 brum, and its relations are entirely with the Automatic apparatus. 



761. When we examine into the relative development of the Cerebellum in 

 the different classes of Vertebrata, we find that it presents some very remarkable 

 differences. 1 In its simpler forms, this organ is found to consist entirely of the 

 representative of the central lobe of the Human Cerebellum, the hemispheres 

 not making their appearance until we have ascended to the class of Birds. The 

 proportional development of the Cerebellum is smallest in the Vermiform Fishes, 

 which approach most nearly to the Invertebrata ; but it is much greater in 

 the higher Cartilaginous Fishes than it is in Reptiles, in which it is generally 

 very low. Passing on to Birds, we remark that the average dimensions of the 

 Cerebellum 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 species which approach most nearly to the Mammalia in general con- 

 formation, such as the Ostrich ; but in those of most active and varied powers 

 of flight. Lastly, on ascending the scale of Mammiferous animals, we cannot 

 but be struck with the rapid advance in the proportional size of the Cerebellum 

 which we observe as we rise from the lowest (which are surpassed in this respect 

 by many Birds) towards Man, in whom it attains a development which appears 

 enormous, even when contrasted with that of the Quadrumana. Now on looking 

 at the size of the Cerebellum in relation to the general motor activity of these 

 classes respectively, and especially taking into account the variety of their 

 respective movements, and the number of separate muscular actions which are 

 combined in each, we can scarcely help noticing that it is in the tribes which are 

 most distinguished in these respects, that the largest Cerebellum is usually found. 



1 The fullest information upon this point will be found in M. Serres's "Anatomic 

 Comparee du Cerveau," and M. Leuret's " Anat. Comp. du Systeme Nerveux." 



