SENSE OF TOUPH. 79 



parts by its internal fase. A considerable number of nerves are 

 distributed in it, and form upon its surface small elevations called 

 papillfe. To these nerves the skin owes its sensibility, which 

 is greatest in those parts where there is the greatrst number of 

 papillae, as in the ends of the fingers for example. 



13. The epidermis is applied upon these nervous pnpilta : it is 

 not itself endowed with sensibility, and renders the sense of touch 

 Jess delicate in proportion to its thickness. Frequent contact 

 with rough and hard substances tends to increase its thickness, 

 thus, the hands of those persons who perform laborious work 

 have the epidermis thicker and less sensible than those whose 

 occupation does not place them in the same circumstances. 



14. Hair, beard, nails, horns, &c., are productions formed by 

 small secreting organs, lodged in the substance of the skin ; they 

 are developed, like the teeth, by the addition of new portions of 

 their substance upon that already firmed, and are not like living 

 organs, the seat of a nutritive movement. We give the name of 

 bulb, to the secreting organs of the h dr and beard. 



15. Finally, there exists in the thickness of the derma, little 

 follicles which secrete the sweat, a liquid which is more or less acid. 



16. The contact of an object with any p->int of the surface of 

 the skin is su indent to determine a sensation there; b-it, that 

 touch may be exercised, it is necessary that the part where this 

 contact takes place shall be so formed as to apply itself exactly, 

 and, in a manner, mould itself to the object which the animal 

 wishes to feel ; this kind of perfected tact has its seat in particu- 

 lar organs called, organs of touch. 



17. In man, the hand is the special organ of touch, and its 

 structure is admirably well adapted to the exercise of this sense. 

 The fineness of the skin, its great sensibility, the species of 

 cushion formed by the subcutaneous fat at the extremities of the 

 fingers, the length and flexibility of these organs and the capabili- 

 ty of opposing the thumb to the other fingers, like a pair ot 

 plyers or forceps, are so many conditions essentially favourable 

 to the delicacy of this sense, and enables us to appreciate with 

 great exactitude the qualities of those bodies we may feel. 



13. Is the epidermis itself sensibl : ? What effort has the thickening of 

 the cuticle upon the -ensibility of a part? 



14. How are hair, beard, horn", nails, (fee. produced ? What name is given 

 Jo the secreting 1 organs of the h;iir and beard? 



15. What is the origin of sweat or perspiration? 



16. Does contact of an object with any part of the skin deternrne sensa- 

 tion a* that part? Is this contact sufficient f r the exercise of the faculty ot 

 touch / 



17. What is the organ of touc'i in mm? Whit are the circumstance! 

 rUich render the hand soadnvrably adapt d to i's purpose ? 



