FUNCTIONS OF THE BRAIN. 63 



feascible and amative in an extraordinary degree, and their 

 sides grow bare with perpetual reilex scratching ; but they 

 show no local troubles of either motion or sensibility. In 

 monkeys not eyen this lack of inhibitory ability is shown, 

 and neither stimulation nor excision of the prefrontal lobes 

 produces any symptoms whatever. One monkey of Horsley 

 and Schaefer's was as tame, and did certain tricks as well, 

 after as before the operation.* It is probable that we have 

 about reached the limits of what can be learned about brain- 

 functions from Ad\dsecting inferior animals, and that we 

 must hereafter look more exclusively to human pathology 

 for light. The existence of separate speech and writing 

 centres in the left hemisphere in man ; the fact that palsy 

 from cortical injury is so much more complete and endur- 

 ing in man and the monkey than in dogs ; and the farther 

 fact that it seems more difficult to get complete sens ^rial 

 blindness from cortical ablations in the lower animals than 

 in man, all show that functions get more specially local- 

 ized as evolution goes on. In birds localization seems 

 hardly to exist, and in rodents it is much less conspicuous 

 than in carnivora. Even for man, however, Munk's way of 

 mapping out the cortex into absolute areas within which 

 only one movement or sensation is represented is surely 

 false. The truth seems to be rather that, although there is 

 a correspondence of certain regions of the brain to certain 

 regions of the body, yet the several parts within each bodily 

 region are represented throughout the ivJiole of the corre- 

 sponding brain-region like pepper and salt sprinkled from 

 the same caster. This, however, does not prevent each 

 * part ' from having its focus at one spot within the brain- 

 region. The various brain-regions merge into each other 

 in the same mixed way. As Mr. Horsley says : " There are 

 border centres, and the area of representation of the face 

 merges into that for the representation of the uj)per limb. 

 If there was a focal lesion at that point, you would have 

 the movements of these two parts starting together." f 



* Philos. Trans., vol. 179. p. 3. 



f Trans, of Congress of Am. Phys. and Surg. 1888, vol. i. p. 343. 

 Beevor and Horsley's paper on electric stimulation of the monkey's brain 

 is the most beautiful work yet done for precision. See Phil. Trans., vol. 

 179, p. 205, esoecially the plates. 



