SKIN-SENSATIONS 



427 



armpit be investigated in the same way, much larger blank 

 areas are met with oval patches more than J inch in diameter. 

 When a hairy surface is tested, it is found that contact with a 

 hair can always be felt ; and when the hairs are shaved, the 

 touch-spots are found to extend around or from the points at 

 which hairs pierce the epidermis. Touchless areas lie between 

 them. Hair-follicles receive tufts of nerve-filaments, and it 

 appears that they are the chief organs of touch. " Touch- 

 corpuscles, " which are found in great numbers in the papillae 



GEANDRY'S CORPUSCLE. 



de. 

 > Space. 



itedCorc. 



Medullary Sheath. 

 JEND-BVLB. 



TO UCH- CORP USCLE. 



FIG. 42. SENSE-ORGANS SUSCEPTIBLE TO PRESSURE. 



All are formed on essentially the same plan ; a fibrous capsule invests a group of epithelial 

 cells amongst which a nerve ramifies. The simplest form is known as a Grandry's cor- 

 puscle a nerve ending in one or two plates between two or three epithelial cells. These 

 organs are found in great numbers in the bills of aquatic birds. If a duck is watched 

 whilst it is gobbling mud at the margin of a pond, it will be seen to have a remarkable 

 capacity for discriminating between the shells of small snails, which it can crush, and 

 stones, which it needs to drop from its bill. Its bill is also provided with small Pacinian 

 corpuscles (Fig. 43). Touch-corpuscles, more elaborate in form than the one figured, are 

 found in the papillae of the skin of the fingers and elsewhere. They appear to be modified 

 hair-follicles. End-bulbs occur in the conjunctiva and elsewhere, and especially in the 

 peritoneum. Together with Pacinian corpuscles, they are accountable for sensations con- 

 nected with the distension of the stomach and intestines. 



of the skin of the fingers and elsewhere, may probably be re- 

 garded as, genetically, hair-follicles which have not developed 

 hairs. 



If sensitiveness to pain is investigated by tapping very gently 

 with a needle or, better, by using a stiff horsehair fixed in a 

 cleft stick, from which it projects about inch it will be 

 found that every here and there are spots which are exceedingly 

 sensitive, whilst adjoining them are areas which are moderately 

 sensitive, and between these areas small spots or stretches of 



