SENSE OF TOUCH 



629 



the delicacy of appreciation of slight impressions, by presenting hard 

 surfaces against which the nerve-filaments can be pressed. 



TABLE OF VARIATIONS IN THE SENSE OF CONTACT IN DIFFERENT 

 PORTIONS OF THE SKIN (WEBER) 



The sensibility is measured by the greatest distance between two points at which they convey a single impression 

 when applied simultaneously. The measurements are given in lines d 1 ^ of an inch, or a little more than 

 2 millimeters). 



As regards those portions of the general cutaneous surface in which 

 no tactile corpuscles have been demonstrated, it is not easy to connect 

 the variations in the sense of contact with the nervous distribution, as 

 little is known of the comparative richness of the terminal nervous 

 filaments in these situations. 



There is much uncertainty in regard to the location of a cerebral 

 tactile centre. Ferrier described a diffused centre in the " hippocampal 

 region," the action of which is crossed ; but the observations to deter- 

 mine loss of the sense of contact after destruction of this part, made on 

 monkeys, are by no means satisfactory. It may be stated provisionally 



