REMOVAL OF BOTH CEREBRAL HEMISPHERES. 703 



process of swallowing. Eventually, it would itself take food if its head 

 were placed over the dish containing it, and especially if the food came 

 in contact with its snout. Meat which had been rendered hitter by 

 quinine or colocynth was ejected with movements indicative of dislike. 

 It also showed a feeling of satiety by refusing to take more than a 

 certain quantity of food. For its size it required a very large amount of 

 nourishment in order to keep up its weight ; the extreme restlessness 

 which it exhibited when awake tending apparently greatly to increase 

 its katabolism. The higher psychical faculties were completely absent. 

 The dog never showed any sign of recognition of persons or of other 

 dogs, showed no fear of threatening movements ; never wagged his tail, 

 or showed any sign of pleasure on being stroked or spoken to ; when 

 wetted, shook himself vigorously but never attempted to lick himself 

 dry, as a normal dog does ; never used his fore-paws to hold a bone or to 

 dig a hole for one (although there was even less paralysis apparent than 

 in animals from which only the sigmoid gyrus is removed) ; never gave 

 any sign of spontaneous mental activity, unless an increased restlessness 

 and other signs of impatience when food was withheld for longer than 

 usual, are to be in a measure so interpreted. The animal showed 

 absolutely no sign of memory. Although its removal from the cage was 

 the usual signal for feeding, it invariably resisted being taken hold of for 

 this purpose, barking loudly and biting and struggling vigorously. 

 During sleep it never showed any indications, as dogs often do, of 

 dreaming. It exhibited no sexual instincts. Eemoval of the hemispheres 

 had produced loss of all understanding and memory ; the condition, in 

 spite of the complexity of many of the phenomena which were still 

 exhibited, was one of complete idiocy ; there was no sign of intelligence, 

 and all the actions of the animal can be explained as reflex responses to 

 immediate excitation. 1 



The result of experiments upon animals tends, therefore, generally 

 to corroborate that of observations upon pathological cases in man ; but 

 it is clear that the higher the position of the animal in the scale of 

 organisation, the more profound is the effect of removing the cerebrum. 

 And it will presently appear that even partial bilateral lesions in 

 monkeys and in man may, in some respects, and according to their 

 extent and position, produce even more marked symptoms of loss of 

 cerebral function, and especially of volitional movements, than in the 

 animals above described. 



There are, as Donaldson points out, 2 anatomical relations behind tin's 

 difference of effect produced by lesions of the hemispheres. For the activity of 

 the lower level cells is in all animals brought about by two sets of impulses — ■ 

 the one set derived from the sensory nerves passing from their terminations 

 in the grey matter of the lower level centres, either directly to the motor cells 

 or more probably through intermediary cells which play an important part in 

 effecting the co-ordination required for purposeful movements. The other set 

 of impulses, also in the first instance derived from the sensory nerves, pass to 

 the cortex, and are thence sent down (perhaps along the fibres of the pyramidal 

 tracts) to the motor nerve cells, or rather probably also to the intermediary co- 

 ordinating mechanism. In the lower animals this second set [days an insig- 

 nificant part in producing the ordinary co-ordinated movements of the animal ; 



1 H. Munk, Verhomdl. d. physiol. Gesellsch. zu Berlin, Arch. f. Physiol., Leipzig, 1894. 

 S. 355. . 



2 "American Text-Book of Physiology," \i. 711. 



