14 psrciioLou v. 



and simple. In a near cliapter we shall return to tlii» 

 controversy again. Let us now look a little more closely 

 at tlie brain and at the ways in which its states may be sup- 

 posed to condition those of the mind. 



THE FROG'S NERVE-CENTRES. 



Both the minute anatomy and the detailed physiology 

 of the brain are achievements of the present generation, or 

 rather we may say (beginning w'ith Meynert) of the past 

 twenty years. Many points are still obscure and subject 

 to controversy ; but a general way of conceiving the organ 

 has been reached on all hands which in its main feature 

 seems not unlikely to stand, and which even gives a most 

 plausible scheme of the way in which cerebral and mental 

 operations go hand in hand. 



The best way to enter the subject will be to take a lower 

 creature, like a frog, and study by the vivisectional method 

 the functions of his different nerve-centres. The frog's 

 nerve-centres are figured in the accompany- 

 ing diagram, which needs no further ex- 

 planation. I will first proceed to state 

 what hap23ens when various amounts of 

 the anterior parts are removed, in different 

 frogs, in the w^ay in w^hich an ordinary 

 student removes them ; that is, with no ex- 

 treme precai^ions as to the purity of the 

 operation. We shall in this way reach a 

 very simple conception of the functions of 

 the various centres, involving the strongest 

 possible contrast between the cerebral 

 no. i.—ci7. Cerebral hemispheres and the lower lobes. This 



Hemispheres: OTIi, -, . •t-i i t t ±' j 



Optic Thalami; O L, sharp COUCeptlOU Will have didactic ad- 

 Optic Lobes; Cb, , i> -i • i<i • i i- 



Cerebellum : M o, Vantages, tor it IS often very instructive 



Medulla Oblongata; , .'..iii • ^ p i j 



s c, Spinal Cord, to start With too Simple a formula ana 

 correct it later on. Our first formula, as we shall later 

 see, will have to be softened down somewhat by the results 

 of more careful experimentation both on frogs and birds, 

 and by those of the most recent observations on dogs. 



