14 ON THE NERVOUS SYSTEM IV. 



more illustration of the inconsistency of this theory (and it equally applies to that 

 of Gall and Spurzheim) with facts ; we will contrast the organ in question, as it 

 appeared to us in the recent dissection of a Porpoise (Delphinus phoctena) and of a 

 Shark (Carcharias obscurus). Both of these animals are predaceous, both pursue 

 their prey in the water, both are endowed with great rapidity of motion, both are 

 capable of readily and suddenly changing their direction, and both move by the 

 alternate flexion and extension of the vertebral column ; I know of no reason for 

 supposing that the power of coordination is materially different in the two ; and in 

 these instances the mass of the body was in the two nearly the same, and yet the 

 cerebellum of the Porpoise is not only relatively, but absolutely, several times larger 

 than the whole encephalon of any known Fish, however large. 



In view of such important opposing facts, derived from comparative anatomy and 

 pathology, and of the contradictory results of experiments, one cannot but enter- 

 tain a doubt that the problem of the functions of the cerebellum is yet solved. 

 The suggestion of Dr. Carpenter, that the middle lobe may be the seat of the 

 sexual instinct, and the lateral lobes of the power of coordination, loses its force 

 when it is remembered, that in Fishes, Reptiles, and Birds even, the lateral lobes 

 either do not exist, or are in a rudimentary condition, entirely disproportioned to 

 the function of coordination. If the size of the organ is any indication of its 

 functional activity, the cerebellum is not proportional to the amount of muscular 

 fibre set in motion, nor yet to the combinations of motions of which animals are 

 susceptible. 



SECTION II. INTERNAL STRUCTURE OF THE BRAIN. 



An indication of imperfect development of the brain in animals is often found in 

 the existence of cavities in one or more of its principal masses. An immature con- 

 dition of one mass, however, by no means involves that of all the others. In some 

 Sharks the nearly solid cerebral lobes accompany a hollow cerebellum, and in 

 other Fishes a solid cerebellum and cerebral lobes, as in the Cod, are associated with 

 optic lobes, which are hollow. In Frogs, with the exception of the cerebellum and 

 optic thalami, all the principal masses are hollow, and in this respect manifest but 

 little progress beyond an embryonic condition. The cavities of the cerebral and 

 olfactory lobes communicate freely with each other, though there is no communica- 

 tion between those of opposite sides. The two lobes above referred to, being de- 

 veloped from the same vesicle, do not manifest any separation from each other until 

 some time after the tadpole leaves the egg, and subsequently the distinction between 

 them is only indicated by a slight constriction. (Fig. 6.) The walls of the cere- 

 bral lobes are quite thin above and externally. On the inner wall may be seen in 

 each ventricle two projections ; the upper and longest corresponding with an external 

 furrow, and which may therefore be regarded, perhaps, merely as a convolution 

 (Fig. 7); and the lower an oval ganglionic body (Fig. 7, C), in which may be seen 

 terminating some of the white fibres prolonged forwards from the spinal chord. 

 This body is solid, and its position in the ventricular cavity, its connection with 

 the white fibres, and its relation to the optic thalami, which are directly behind 



