900 



TEE SENSORY APPARATVSES. 



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

 tions termed pajiilUB, 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 



Fig. 482. 



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



E, Epidermis; D, Jerma. 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. 



Fig. 483. 



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

 to endow these apertures with their 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 fonn the reticular layer {stratum 

 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 ;;r//?//- 

 lanj layer {stratum papillare), the superficial limit 

 of which forms an amorphous layer (basal membrane). 

 The papiUce 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 ^\-^ to ■^\s of an inch in length, and fi'om -^^-g to -g^ of an inch 



CAPILLARY LOOPS IN THE CUTA- 

 NEOUS PAPILLAE OF THE LIPS. 



