Our knowledge of the localization in the brain of its various functions is still far from perfect. Much of the experimentat ion upon cerebral localization has been done upon the monkey by exposing the brain and electrically stimulating its surface. The work of Ferrier along this line has been of extreme importance. By electrically stimulating the cortex in the monkey he deter mined the area stimulation of which caused mo tion of some part of the body, and, by comparing the convolutions of the monkey's brain with those of the human brain, he determined the probably analogous areas. The results may be briefly summed up as follows: There is it considerable area having the fissure of Rolando for its central line. Which is known as the general sensory nadlir area. The inotor of this area are well shown in the aceomiranying diagrams. Stim ulation of other parts of the brain failed to elicit any reaction. The sensory areas are not Si) well defined. and for reasons are much more difficult of determination. IVithill this same region arc probably located the areas which have to do with general sensations. The special senses have, however. special localizations. Thus the cortical visual centre 'is situated in the oeci pital lobe. the centre for the conscious appreeia tion of sound (hearing centre) in the front and upper part of the temporal lobe, while the sense of smell is located below the latter in the tip of the temporal lobe.
That the frontal lobes are most concerned in the higher intellectual activities has long been believed. Stimulation of these lobes causes no reaction. According to Ferrier their complete removal causes no sensory or motor disturbances, description of the monkey after complete re inoval of the frontal lobes is as follows: "The animals retain their appetites a»d instincts and are capable of exhibiting emotional feeling. The
sensory faculties—sight, hearing. touch, taste. and smell—remain unimpaired. The powers of voluntary motion are retained in their integrity and there is little to indicate the presence of such an extensive lesion or the removal of so large a part of the brain. And vet. notwith standing this apparent absence of physiological symptoms. 1 could perceive a very deeided altera tion in the animal's character and behavim., though it is diffieult to slate in precise terms the nature of the elialtge. The animals operated on were ?I'ket1.11 on IlVe011111 of their intelligent character. After the operation. though they might seem to one who had not compared their pre,Hit. with the past fairly lip to the average of monkey intelligenee, they had undergone a eon siderable psychologieal alteration. Instead of. as before, actively interested in their sur• rounding.. and curiously prying into all that cattle Within the field of their observation. they remained apathetic or doll, or dozed off to sleep, responding only to sensations or impressions of the moment, or varying their listlessness with restless and purposeless wanderings to and fro. While not actually deprived of intelligence. they had lost to all appearance the faculty of attentive and intelligent observation." The separate localization of the different emo tions, such as bate, love, fear, etc., which the teachings of phrenology would lead one to expect, has never been accomplished. In fact, there is every reason to believe that no such localization exists, the same parts of the cortex being con cerned in very different emotions,