FUNCTIONS OF THE BRAIN. 43 



them for comparison. They did not pick up food strewn 

 on the ground, however. Schrader found that they would 

 do this if even a small j^art of the frontal region of the 

 hemispheres was left, and ascribes their non-self-feeding 

 when deprived of their occipital cerebrum not to a visual, 

 but to a motor, defect, a sort of alimentary aphasia.* 



In presence of such discord as that between Munk and 

 his opponents one must carefully note how differently sig- 

 nificant is loss, ivom preservation, of a function after an oj)era- 

 tion on the brain. The loss of the function does not neces- 

 sarily show that it is dependent on the part cut out ; but its 

 'preservation does show that it is not dependent : and this is 

 true thoagh the loss should be observed ninety-nine times 

 and the preservation only once in a hundred similar excisions. 

 That birds and mammals can be blinded by cortical abla- 

 tion is undoubted ; the only question is, must they be so ? 

 Only then can the cortex be certainly called the * seat of 

 sight' The blindness may always be due to one of those 

 remote effects of the wound on distant parts, inhibitions, 

 extensions of inflammation,— interferences, in a word, — 

 upon which Brown-Sequard and Goltz have rightly insisted, 

 and the importance of which becomes more manifest every 

 day. Such effects are transient ; whereas the symptoms of 

 deprivation {Aiisfallserscheiniingen, as Goltz calls them) which 

 come from the actual loss of the cut-out region must from 

 the nature of the case be permanent. Blindness in the 

 pigeons, so far as it passes aicay, cannot possibly be charged 

 to their seat of vision being lost, but only to some influence 

 which temporarily dejDresses the acti\^ty of that seat. 

 The same is true mutatis mutandis of all the other effects of 

 operations, and as we pass to mammals we shall see still 

 more the importance of the remark. 



In rabbits loss of the entire cortex seems compatible 

 with the j3reservation of enough sight to guide the poor 

 animals' movements, and enable them to avoid obstacles. 

 Christiani's observations and discussions seem conclusively 



* PHligcr's Anhiv, vol. 44, p. 176. Munk (Berlin Academy Sitzsiings- 

 bcrichte, 18."59, xxxi) returus to the charge, denying the extirpations of 

 Sciuader to be complete: "Microscopic portions of the Sehsphdre must 

 remain. " 



