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A MANUAL OF PHYSIOLOGY 



physiological hierarchy. A more minute analysis shows us 

 that the cerebral cortex itself is not homogeneous in function, 

 that certain regions of it have been set aside for special 

 labours. Our knowledge of this localization of function in 

 the cerebral cortex has been derived partly from clinical, 

 coupled with pathological observations on man, and partly 

 from the results of the removal or stimulation of definite 

 areas in animals. And so varied and extensive have been 

 the contributions from both of these sources, that it is 

 difficult to decide to which we owe most. 



It is a fact which might 

 appear strange and almost 

 inexplicable did the history 

 of science not constantly 

 present us with the like, 

 that thirty years ago the 

 universal opinion among 

 physiologists, pathologists, 

 and physicians was that the 

 cerebral cortex is inexcit- 

 able to artificial stimuli, 

 that no visible response 

 can be obtained from it. 

 The great names of Flourens 

 and Magendie stood spon- 

 sors for this error, and re- 

 pressed research. In 1870, 

 however, Hitzig and Fritsch 

 showed that not only was 

 FIG. 264'. MOTOR AREAS OF DOG'S BRAIN, it possible to elicit muscu- 

 n, neck ;//., fore-limb ; h.l., hind-limb ; /, tail; lar contractions by Stimula- 

 /, face; c.s., crucial sulcus; e.m., eye movements; f - r f L rnr . PY n f t u p 



p. dilatation of the pupil in both eyes, but especially J 1 



in the opposite eye. All the areas are marked in brain in the dog With voltaic 

 the figure only on the left side except the eye currents, but that the ex 

 areas, whose position, to avoid confusion, is in- r : ffl ui p flrpa nrmnipH a 

 dicated on the right hemisphere. uuauic area occupied 



definite region in the 



neighbourhood of the crucial sulcus, which runs out over the con- 

 vexity of the hemispheres nearly at right angles to the longitudinal 

 fissure. In this region they were further able to isolate several 

 distinct areas, stimulation of which was followed by movements 

 respectively of the head, face, neck, hind-leg, and fore-leg. This 

 was the starting-point of a long series of researches by Ferrier, 

 Munk, Horsley, Schafer, Heidenhain, and many others, on the 

 brains of monkeys, as well as dogs researches which have formed 

 the basis of an exact cortical localization in the brain of man, and 

 have enriched surgery with a new province. In these later experi- 

 ments the interrupted current from an induction machine has been 



