x THE FOKE-BKAIN 583 



section (Chap. V. pp. 341 et seq.). Notwithstanding this cutaneous 

 hyperaesthesia, the animal cannot use its muscles in carrying out 

 certain voluntary acts. It feeds clumsily and dirtily like a pig, 

 making unusual associated movements both with its limbs and 

 with its jaws and tongue. It can only pick up a bone with its 

 mouth after many attempts and with great trouble, and is quite 

 incapable of holding it between the front paws, like a normal dog, 

 to gnaw it. If accustomed, before the operation, to giving its paw, 

 the power of doing so seems entirely lost. If a piece of meat is 

 offered to it so that the long axis of the head has to be raised to 

 90, the animal is incapable of making this movement ; it opens 

 and shuts its mouth in the direction of the food without power 

 to take it, or to direct the position of the head so that the meat 

 should drop into its mouth. 



Another interesting result of Goltz' researches is that dogs 

 whose anterior cerebral lobes have been extensively mutilated on 

 both sides lose the power of voluntarily controlling the reflexes, 

 the centres of which lie in the bulbo-spinal axis. Goltz described 

 a series of characteristic reflex movements which are almost 

 constant in normal dogs on gently exciting the skin in certain 

 regions, and he observed that these reflexes not only persisted but 

 were exaggerated in dogs that had been operated on. In relation 

 to this diminished power of voluntary inhibition, expressed in the 

 apparent rise of reflex excitability, is the fact pointed out by 

 Goltz that dogs after removal of the anterior part of the hemispheres 

 become more impulsive and aggressive. Animals that had been 

 docile, quiet, and affectionate, became difficult to manage, ill- 

 tempered, and abnormally restless after the operation, and continued 

 so for months, till progressive emaciation led to death. 



These facts show that the symptoms of sensory-motor paralysis 

 or paresis directly due to extirpation on one or both sides of the 

 anterior parts of the hemispheres diminish gradually till they 

 disappear to a large extent. The residual defect phenomena 

 persist till death, and consist in the animal's imperfect capacity for 

 acquainting itself with the position and form of objects by means 

 of the muscular and cutaneous senses, for using its muscles as 

 in the normal performance of certain voluntary acts, and ifor 

 voluntary inhibition. We shall presently return to this pheno- 

 menon in order the better to define it from the psycho-physiological 

 'point of view. 



Having thus examined the effects of total destruction of the 

 part of the brain which contains the excitable area, we must next, 

 by the method of electrical stimulation, investigate the effects of 

 extirpating the cortex only of certain of the lobules or centres into 

 which it can be divided. 



Munk divided the excitable area which he termed the 

 " sensory sphere " because he regarded it as the seat of the 



