706 



TOPOGRAPHY OF THE MOTOR CENTRES. 



apparatus, which, however, is not injured anatomically; this may be explained in the same way 

 as the suppression of reflexes by strong stimulation of sensory nerves ( 361, 3). In addition, 

 there are the permanent phenomena, due to the disappearance of the activity of the nervous 

 apparatus, which is removed by the operation. A dog, with a large mass of its cerebral cortex 

 removed, may l>e compared to an eating, complex, reflex machine. It behaves like an intensely 

 stupid dog, walks slowly, with its head hanging down ; its cutaneous sensibility is diminished 

 in all its qualities it is less sensitive to pressure on the skin ; it takes less cognisance of 

 variations of temperature, and does not comprehend how to feel ; it can with difficulty 

 accommodate itself to the outer world, especially with regard to seeking out and taking its food. 

 On the other hand, there is no paralysis of its muscles. The dog still sees, but it does not 

 understand what it does see ; it looks like a somnambulist, who avoids obstacles without 

 obtaining a clear perception of their nature. It hears, as it can be wakened from sleep by a 

 call, but it hears like a person just wakened from a deep sleep by a voice such a person does 

 not at once obtain a distinct perception of the sound. The same is the case with the other 

 senses. It howls from hunger, and eats until its stomach is filled ; it manifests no symptoms 

 of sexual excitement. 



Ooltz supposes that every part of the brain is concerned in the functions of willing, feeling, 

 perception, and thinking. Every section is, independently of the others, connected by con- 

 ducting paths with all the voluntary muscles, and, on the other hand, with all the sensory nerves 

 f the body. He regards it as possible that the individual lobes have different functions. 



After removal of the anterior or frontal convolutions and the motor areas, there is at first 

 unilateral motor and sensory paralysis and affection of vision. After some months, there remains 

 only the loss of the muscular sense. If the operation be bilateral, the phenomena are more 

 marked ; there are innumerable purposeless associated movements, and the dogs become 

 vicious. Marked and permanent disturbance in the capacity to utilise the impressions from the 

 sense-organs is not a necessary consequence of removal of the frontal convolutions. 



Removal of the occipital lobes interferes most with vision. Bilateral removal makes the 

 animal almost blind. The dog remains obedient and lively. There is no disturbance of motion 

 or of the muscular sense. 



Inhibitory Phenomena. Injury to the brain also causes inhibitory phenomena, such as the 

 disturbances of motion, the complete hemiplegia which is frequently observed after large 

 unilateral injuries of the cortex cerebri ; these ace regarded by Goltz as inhibitory phenomena, 

 due to the injury acting on lower infra-cortical centres, whose action inhibits movement, but 

 these movements are recovered as soon as the inhibitory action ceases. 



378. TOPOGRAPHY OF THE CORTEX CEREBRI. A short resume of 

 the arrangement of convolutions, aceordiug to Ecker, is given in 375. 



I. The cortical motor areas for the face and the limbs are grouped around the 



Fig. 488. ' Fig< 489> 



Fig. 488. Motor areas in man shaded outer surface of the left side of human brain. Dotted 

 area, the aphasic region (modified from Cowers). Fig. 489.-Inner surface of right hemi- 

 sphere. AS,*xe* governing the movements of the arm and shoulder ; TV, of the trunk ; 

 ocri itaMobe gys fomicatus ; CC, corpus callosum ; U, uncinate gyrus; 0, 



fissure of Rolando, including the ascending frontal, ascending parietal, and part of 

 the parietal lobule (fig. 488). The centre for the face occupies the lowest third of 

 the ascending frontal convolution, and reaches also to the lowest fifth of the ascend- 

 ing parietal. The arm centre occupies the middle third of the ascending frontal and 



