S 02 TEXT-BOOK OF PHYSIOLOGY. 



of this convolution was followed by hemianesthesia of the opposite 

 side of the body which was more or less marked and persistent. 

 These observers conclude that the limbic lobe "is largely if not 

 exclusively concerned in the appreciation of sensation, painful and 

 tactile." Other experimenters question this conclusion and locate 

 the area near to, if not within, the Rolandic area. The difference of 

 opinion regarding the location and probable limitation of the area 

 of tactile sensibility renders necessary additional and more conclusive 

 experiments. 



The oljactory and gustatory areas or areas of olfactory and gusta- 

 tory perception have been located in the uncinate gyrus and the 

 adjacent region, though their exact limits have not been determined 

 by the experiments thus far performed. 



The auditory area or area of auditory perception was located by 

 Ferrier in the upper two-thirds of the superior temporo-sphenoidal 

 convolution. Bilateral cauterization of this region gave rise to com- 

 plete deafness, which endured to the time of the animal's death, 

 more than a year later. Unilateral destruction of this region gave 

 rise to deafness in the opposite ear only. The results of experiments 

 made subsequently by other observers would indicate that the audi- 

 tory area is somewhat more extended than that designated by Ferrier, 

 as apparently animals recovered their hearing, to some extent at 

 least, after complete recovery from the operation. The limit or 

 extension of the area is, however, uncertain. 



The visual area or area of visual perception has been located in 

 the occipital lobe, though in this, as in the previous instances, its 

 exact limits have not been positively determined. Experimenters 

 also are not in accord as to the relative functions of its different parts. 

 Ferrier located this area in the occipital lobe and that adjacent por- 

 tion of the parietal lobe on the outer surface known as the angular 

 gyrus. He found that extirpation of the angular gyrus alone was 

 followed by a temporary blindness of the opposite eye, which was, 

 however, not hemiopic in character.* He also found that destruction 



* In a consideration of this subject certain facts connected with visual perception, 

 both in physiologic and pathologic conditions, must be kept in mind. Thus, 

 visual sensation may arise from stimulation of either the central portion, the macula, 

 or the peripheral portion of the retina or both. In the first instance the vision is 

 termed central or macular; in the second instance, peripheral or retinal. Macular 

 vision is clear, sharp, and distinct; retinal vision progressively indistinct from the 

 center toward the periphery. Division of one optic tract is followed, in consequence 

 of the partial decussation of the optic nerve-fibers at the chiasma, by a loss of function 

 in the outer two-thirds of the retina of the same side, both in the central (macular) 

 as well as in its peripheral portions, and the inner one-third of the retina of the oppo- 

 site side. To this condition the term hemiopia has been applied. As a result of this 

 want of functional activity of these retinal portions on the side of the lesion, rays 

 of light emanating from objects situated in the opposite side of the -field of vision will 

 not be perceived when both eyes are directed to the fixation point. To this "blind- 



