REMOVAL OF BOTH CEREBRAL HEMISPHERES. 701 



may look up, yawn, shake itself, dress its feathers with its beak, move a 

 few steps, and then settle down quietly, standing sometimes on one foot 

 and sometimes on both. Should a fly happen to settle on its head, it 

 will shake it off. If ammonia be held near its nostrils, it will start back. 

 Should the finger be brusquely approximated to its eyes, it will wink and 

 retreat. A light flashed before its eyes will cause the pupil to contract ; 

 and if a circular motion be made with the flame, the animal may turn 

 its head and eyes accordingly. It will start suddenly and open its eyes 

 widely if a pistol be discharged close to its head." 



" After each active manifestation called forth by any of these 

 methods of stimulation, the animal again subsides into its state of 

 repose. It makes no spontaneous movements. Memory and will seem 

 annihilated. When irritated it may show fight both with wings and 

 beak, but it exhibits no fear and makes no attempts at escape. It 

 resists attempts to open its beak for the purpose of introducing nourish- 

 ment, but, should its resistance be overcome, it swallows as usual. If 

 fed artificially it may be kept alive for months, but left to itself it will 

 die of starvation, like the frog or fish." l 



But in the bird also, 2 if care be taken to remove only the cerebral 

 hemispheres and basal ganglia without injury to the optic lobes or 

 nerves, not only are spontaneous movements frequently manifested, but 

 the animal (pigeon) gives indication that its movements are guided by 

 visual impressions. Thus in the light or in day-time the animal walks 

 continually about the room, 3 avoiding all obstacles, 4 even if transparent, 

 such as glass objects, but in the dark remains quiescent and apparently 

 asleep. It will even fly a little, so as to surmount small obstacles. 

 There is sufficient understanding of things seen for selection of a sort to 

 be exercised ; Schrader found that his pigeons preferred to alight upon a 

 perch to the floor ; but they hardly ever flew spontaneously up from the 

 floor on to a perch. 5 Food, however, is not recognised, nor are enemies 

 nor individuals of the opposite sex, although certain sexual phenomena, 

 e.g. the cooing of the male bird, are retained. The animal manifests no 

 fear. It responds mechanically to stimuli, like an automaton. If placed 

 on a swinging cord, it balances itself perfectly with the to-and-fro 

 movements, and this may be kept up for an hour or more; if then 

 placed on the floor it still continues the balancing movements for a 

 time. H. Munk 6 found that pigeons deprived of their hemispheres 

 were completely blind, but it would appear that whilst blind, in the 

 sense of failing to comprehend the significance of objects, such animals 

 will react to visual impressions through the medium of the optic lobes. 

 In owls and falcons Schrader 7 found much more marked disturbances 

 of mobility, especially of the hind-limbs, after ablation of the hemi- 

 spheres (or even of the anterior part only) than is the case with pigeons. 

 It is noteworthy that these birds of prey employ their feet like hands 

 to seize and hold their food, and their movements are therefore 



1 Ferrier, loc. cit. 



2 Schrader, Arch. f. d. ges. Physiol., Bonn, 1888, Bd. xliv. S. 175. 



3 Voit, Sitzungsb. d. math.-phys. Cl. d. Ic. -layer. Akad. d. Wissensdi. zu Mi'mchen, 1868, 

 S. 105. 



4 Renzi, " Saggio di fisiol. sperim. sui centri nervosi," Ann. univ. dimed. e chir., Milano, 

 1863, tomo clxxxvi. p. 179; ibid., 1894, tomo clxxxvii. p. 59 ; Schrader, loc. cit. 



5 Cf. M'Kendrick, " Recent Researches on the Nervous System," Edinburgh, 1874. 

 "Functionen d. Grosshirnrinde, " Berlin, 1890, S. 279. 



7 " Zur vergl. Physiol. d. Grosshirns," Strassburg, 1890. 



