RELATIVE ACUTENESS OF SENSE OF TOUCH. 2 19 



of the hand, the cheek, and the eyelids, five lines; the 

 palate, six lines; the prominence of the cheek, and the sole 

 of the foot near the great toe, seven lines; the back of the 

 hand near the fingers, eight lines ; the gums, nine lines ; the 

 lower portion of the forehead, ten lines; the lower part of 

 the occiput, twelve lines; the back of the hand, fourteen 

 lines; the throat under the jaw, fifteen lines; the shoulder, 

 fore-arm, and knee, eighteen lines; the chest over the 

 sternum, twenty lines ; the loins, the upper part of the back, 

 and the neck on the line of the spine, twenty-four lines; 

 the middle of the back, of the neck, of the arm, and of the 

 thigh, thirty lines. ' 



Gratiolet found by oft-repeated experiments that the dis- 

 tances recognized by the pulp of the fingers might be very 

 much less. By touching two points on the same papillary 

 ridge on the pulp of the last joint of the middle finger, sepa- 

 rated only by the orifice of a sudoriferous duct, the two sen- 

 sations were plainly distinguished at the distance of less than 

 one quarter of a line. 



The experiments of Valentin, on the other hand, prove 

 that tactile sensibility varies from single to double in cor- 

 responding regions in different individuals; we can only 

 accept the measurements of Weber, therefore, as indicating 

 the relative sensibility. And lastly, we are indebted to M. 

 Belfield-Lefevre for the experiments which led him to the 

 following conclusions. The distance between two points of 

 contact is better appreciated, if these points are placed on a 

 line transverse to the axis of the body, than when on a line 

 parallel to it or longitudinal. According to Weber, on the 

 ends of the fingers, and on the tip of the tongue, the distance 

 is better appreciated on a longitudinal than on a transverse 

 line. The distance between two points of contact, distinct 

 and simultaneous, is greater in proportion to the delicacy of 

 feeling in the region experimented on; it seems to be greater 

 also when the contact takes place successively in the two 

 points, than when it takes place simultaneously, and greater 

 also if the two contacts are separated by a longer interval of 

 time. If the two points of contact are separated by the 

 median line, the distance between them seems greater than 



