COMPARATIVE ANATOMY. 



mind more vigorous and more clearly de- 

 veloped. In this point of view man is 

 decidedly pre-eminent : here he excels 

 all other animals that have hitherto been 

 investigated. 



All the simix, says Sommerring, are 

 placed far behind man in this respect. 

 Although the brain in some instances, 

 particularly among the smaller kinds, 

 which have prehensile tails, is larger in 

 proportion to their body than that of the 

 human subject ; yet a very large share of 

 that brain is required for the immense 

 nerves which supply their organs of sense 

 and mastication. Let us remove that por- 

 tion of the brain, and a very small quan- 

 tity will remain. 



The researches of the same author on 

 animals in general have led him to con- 

 clude, that the quantity of brain, over 

 and above that which is necessary for a 

 mere animal existence ; that part, in short, 

 which is devoted to the faculties of the 

 mind, bears a direct ratio to the docility 

 of the animal, to the rank which it would 

 hold in a comparative scale of mental 

 powers. 



The largest brain, which Sommerring 

 has found in a horse, weighed \lb. 4oz. 

 and the smallest, which he has seen in an 

 adult man; was 2/. 5oz. Yet the nerves 

 arising from the former brain were at 

 least ten times larger than those of the 

 latter. 



Generally speaking, small animals have 

 a larger brain in proportion to their body 

 than larger ones. The pachydermata have 

 it very small; and in red-blooded animals, 

 its size is very trifling when compared 

 with the body. 



of the 



Chaffinch - - - 

 Redbreast - - - 

 Blackbird - - - 

 Canaryt/ird - - - 



Cock 



Duck - - - - 

 Goose 

 Tortoise 

 Turtle - - - 

 Coluber natrix 

 Frog - - - 

 Shark - - - 

 Pike .... 

 Carp - - - - 



f 



2T 



- " -sh 



TToT 

 jlo 



Many mammalia possess a bony tento 

 rium cerebelli. It is difficult to give a 

 physiological explanation of the use of 

 this bony tentorium. The opinion which 

 has been generally adopted by anatomists, 

 that the structure in question belongs to 

 such animals only as jump far, or run 

 with great velocity, and that it serves the 

 purpose of protecting the cerebellum 

 from the pressure of the cerebrum in these 

 quick motions, is obviously unsatisfactory. 

 It exists in the bear, which is not dis- 

 tinquished for its activity ; while several 

 animals which excel in jumping or spring- 

 ing do not possess it ; viz. the wild goat, 

 (capra ibex.) Cheselden ascribes it to 

 predaceous animals only, ('* Anat. of the 

 Bones," cap. 8 ;) but it exists in several 

 others. 



We have given these remarks on the 

 generally assigned use of the bony tento- 

 rium, because a similar mechanical ex- 

 planation has been assigned of the falx, 

 and the tentorium of the human subject ; 

 viz. that the former protects the hemi- 

 spheres from mutual pressure, when the 

 person lies with his head resting on one 

 side ; and that the latter provides against 

 the compression of the cerebellum by the 

 superincumbent cerebrum. These ex- 

 planations are assigned in the present, 

 day by anatomists of such distinguished 

 reputation as Sommerring and Cuvier 

 (" de Corporis Humani Fabrica," vol. 4, 

 p. 27. " Lcons d'Anat. compar." torn. 

 2, p. 178.) If the futility of this piece 

 of physiology werenotsufficiehtly proved, 

 by considering that the cranium is accu- 

 rately filled, and that there is conse- 

 quently no room for its contents to fall 

 from one side to the other, it must im- 

 mediately be rendered manifest by Mr. 

 Carlisle's case; in which the falx was 



