THE BRAIN 719 



disturbance of smell or taste. The animal was more docile than 

 before the operation, and showed no longer any inclination to play 

 with its companions. To a stranger, however, it appeared no less 

 intelligent than a normal dog. 



In apes (Macacus rhesus), the effects of total extirpation of both 

 hemispheres are exceedingly severe. In a series of experiments 

 recently reported, only one animal out of seventeen lived any length 

 of time (twenty-six days). In this case, an interval of forty-four 

 days elapsed between the removal of the first and second hemispheres. 

 As a result of the operation, the movements of the head and eyes 

 were in many animals apparently unaffected; the movements of the 

 extremities, on the other hand, were severely impaired, in some 

 cases there was marked tonic contraction. Tactile stimulation, 

 such as stroking or blowing, produced raising of the head, opening 

 of the eyelids, widening of the pupils, and some movement of the 

 limbs Stimulation by light, even intense, produced but a slight 

 reaction of the pupils. Noises induced movement of the ears and 

 eyelids, and caused the body to be drawn up together. The animals 

 made noises, but showed no signs of mimicry. They exhibited periods 

 of sleep and wakefulness. When asleep, they had their eyelids firmly 

 closed, made no spontaneous movement or sound, and did not respond to 

 stimulation such as would arouse a normal animal. In one case only were 

 swallowing movements observed when liquid nourishment was given. 



The removal of one hemisphere, on the other hand, had surprisingly 

 little effect A few hours after the operation the animal sat up, 

 seized food, ate, and climbed, although there was marked paresis of the 

 limbs of the opposite side. Then followed a period of drowsiness, but 

 after three or four weeks it was difficult by superficial observation to 

 tell such an animal from a sound one. Upon examination, the limbs of 

 the opposite side showed a certain degree of paresis, more marked in 

 the upper than in the lower limb, hand and finger movements being 

 more affected than elbow or shoulder movements. Head movements, 

 hardly disturbed by the operation, soon became perfectly normal. 

 In regard to sensation, there was at first, at any rate in some of the 

 animals, a, tiyperaesthesia of the opposite side. Eventually, all animals 

 showed .some degree of diminished sensibility, but reacted to strong 

 stimuli. All the animals showed a marked, lasting disturbance of vision 

 (hemianopia). The pupil light reflex remained normal, and the eye 

 movements undisturbed. No disturbance of hearing could be demon- 

 strated It made no difference which hemisphere was extirpated, 

 but in two cases, after extirpation of the left hemisphere, an impression 

 was obtained that the left hand was not so skilled as the right had been. 

 In all cases the completeness of the removal was proved post mortem. 

 The caudate and lenticular nuclei and the optic thalamus were for the 

 greater part destroyed. 



Recently there has been described the case of a child which lived 

 three and three-quarter years without cerebral hemispheres. These 

 had been reduced to thin- walled cysts. No trace of nerve-fibres 

 was found in the part of the brain corresponding to the neo-encephalon. 



