900 



THE SENSORY APPARATUSES. 



the surface of the skin ; this external face also shows a multitude of little eleva- 

 tions termed papilJce, in which the majority of the nerves terminate. 



The derma is not of the same thickness everywhere, being much thinner 

 where it is protected from external injury — as on the under-surface of the belly, 

 the inner side of the legs, thighs, etc. ; it is also thin around the margin of the 



SECTION OF horse's SKIN (FROM WING OP THE NOSTRIL). 



E, Epidermis ; D, derma. 1, Horny layer of the epidermis ; 2, stratum mucosum ; 3, papillary layei 

 of the derma ; 4, excretory duct of a sudoriparous gland ; 5, glomerule of a sudoriparous gland ; 

 6, hair-follicle ; 7, sebaceous gland ; 8, internal sheath of the hair-follicle ; 9, bulb of the hair ; 

 10, mass ot adipose tissue. 



natural openings, to permit the transition between the two membranes, and 

 to endow these apertm-es with theu- necessary dilatability. 



Structure. — The derma is composed of fasciculi of connective tissue inter- 

 woven and matted in a solid manner, and in the meshes of which are some 

 smooth muscular fibres, which, by their contraction, produce the condition of 

 the skin known as the cutis anserina (goose-skin). Somewhat loosely woven in 

 its deepest part to form the reticular layer {stratum 

 Fig- -193. reticulare), the derma contains the roots of the hair- 



follicles, the sudoriparous (or sweat) glands, and 

 small masses of adipose tissue ; superior, its 

 structure is very condensed, to constitute the papil- 

 lary layer {stratum papilJare), the superficial Umit 

 of which forms an amorphous layer {basal membrane). 

 The papilke are of two kinds — vascular and 

 nervous, and are regularly arranged in parallel series. 

 They are most numerous in those parts of the skin 

 especially destined for the exercise of touch— as at 

 the lips, in the keratogenous membrane (of the 

 foot), and other parts where sensibility is very acute — such as the scrotum, sheath, 

 and integuments of the penis. The papillary prolongations of the derma are 

 conical or fungiform, and pediculated ; their dimensions are very variable ; 

 measuring from -j--^ to -^ of an inch in length, and from y-^ to ^^ of an inch 



CAPILLARY LOOPS IN THE CUTA- 

 NEOUS PAPILLA OF THE UPS. 



