228 INITIATIVE IN EVOLUTION 



thesis here put forward for me to appeal to the authority of the 

 facts contained in the tables for such evidence as they can give, 

 and to give a summary of this. 



Summary. 



1 . Table I. shows that the structures known as touch corpuscles 

 are distributed on those parts of the skin where the stimuli of touch 

 fall most and in proportion to the degree in which those parts are 

 employed in tactile discrimination ; thus, most of all on the index 

 finger (with the exception of the tip of the tongue) next on the 

 thumb and less on the middle finger. There are 530 of these 

 corpuscles to the upper and 317 to the lower extremity. 



2 . Table II. bears out the same conclusion, the average number 

 of corpuscles to a square millimetre being twenty-one on the 

 terminal, eight on the second and four on the first phalanges of the 

 index finger, whereas on the foot there are seven on the great 

 toe much exposed to stimuli and only two on the middle of the 

 sole of the foot, which is little exposed. The absence of them 

 from the cornea and conjunctiva, protected by quick and powerful 

 reflexes from such stimuli, and from the (normally) covered glans 

 penis is in accordance with the other results. 



3. Table III. dealing with touch spots, shows that these are 

 nearly twice as numerous on the flexor as the dorsal surface of the 

 forearm ; and nearly five times as numerous as on the scalp, where 

 tactile stimuli are few, and that the distal phalanx of a finger 

 contains about seven times as many as an area between the 

 shoulders. The regions poor in touch spots are shown to be those 

 where relatively few tactile stimuli can fall. 



4. Table IV. gives cold and warmth sensations graded according 

 to the delicacy with which they are perceived in many regions of 

 the skin. The cold sensations are best distinguished on the parts 

 normally most exposed to cold, as the tips of fingers, malleoli, 

 tip of nose, chin, patella, wrist, and least on the protected areas, 

 inner side of thigh, flank, loins and abdomen . The warmth sensations 

 are best distinguished on the regions on which the stimuli of warmth 

 has most frequently fallen, tips of fingers and toes, cavity of mouth, 

 palm of hand, less so on the neck and loin. And the striking fact 

 is noted that warmth sensations are not felt in the lower gums, 

 the inside of the cheek at a certain level and the cornea, which 

 again is protected from these stimuli by its efficient reflex, whereas 

 to the gums and inside of the cheek most warmth stimuli have 

 not been "stimuli " at all. 



