410 INNERVATION. [CHAP. xiv. 



separated from one another. In gradually tearing off the epi- 

 dermis, the foregoing account of the arrangement of the papillae 

 may be fully verified with the aid of a pocket lens. They are 

 seen to form a' close pile on the surface of the chorion, each one 

 being lodged in a separate cavity in the deep surface of the cuticle. 

 The papillae are not equal in size, but frequently a small one is 

 joined with a large one : and the clefts left between them, by the 

 removal of the epidermis, are unequal likewise ; those between the 

 rows being deepest, and those between the individuals of a pair 

 being commonly shallower than those between the pairs. This 

 subordination corresponds (though not accurately in degree) with 

 that of the grooves on the outer surface of the cuticle, where the 

 shallow intervals between the individuals of a pair are not even 

 visible at all, being lost by the thickness of the superimposed sub- 

 Fig 80 stance. Such is the exactness 



of the impression or mould of 

 v|i^||\ the papillary structure which 

 - ;| a the under-surface of the epi- 



* dermis presents, that it fur- 



^ nishes an excellent test of the 

 amount and complication of 

 the former structure in dif- 

 ^f JS'""" ^ ferent regions of the skin. 



v - > ^iijjjji This WU< 1 be seen by compar- 

 Xm ? ^i ing figs. 79 and 80 ; the latter 

 of which, taken from the cu- 

 ticle of the leg, represents the 



Under-surface of the cuticle, from the leg: a. , ,, , . 



Small creases or furrows, b. Shallow depressions for SnallOW depressions into 



the papillary structure, c. Epithelium of sudoriferous ,-, /. -i /. .11 



ducts, corresponding to those in fig. 79. Magn. 30 diam. tne 16 W Clwari papillary 



tions of the cutis in that part have been received. The gradations 

 of size in the papillary structure can be everywhere admirably 

 traced in this way ; and will be found to correspond accurately 

 with the account of the relative acuteness of the sense of touch in 

 different parts, deduced from experiments, which will be subse- 

 quently given. 



The papillae are of an average length in man of y-J-g- of an inch ; 

 at their base, where they spring from the cutis, they measure 

 about -2%-Q of an inch in diameter, and they taper off to a slightly 

 rounded point. They are semi-transparent and flexible ; but suffi- 

 ciently firm in texture to resist maceration long, and not readily to 

 admit of being detached from the cutis. Viewed, when fresh, with 

 a high microscopic power, their outline is definite and sharp, and 



