662 



OF SECRETION. 



[Fig. 263. 



[Fig. 265. 



Vertical section of the skin 

 and sweat-glands of the axilla; 

 a. Layer of glands with their 

 ducts traversing*, the cutis and 

 cuticle, c. Small hair, d, d. 

 Portions of larger hairs. 

 Magn. one and a half diam.] 



[Fig. 264, 



f 



Sweat-gland and the commencement of its 

 duct : a. Venous radicles on the wall of the 

 cell in which the gland rests. This vein anas- 

 lomoses with others in the vicinity, b. Capilla- 

 ries of the gland separately represented, arising 

 from their arteries, which also anastomose. 

 The blood-vessels are all situated on the outside 

 or deep surface of the tube, in contact with the 

 basement-membrane. Magn. 35 diam.] 



a. Vertical section of the cuticle from the heel, 

 detached by maceration. The epithelium of the 

 sweat-duct, continuous with the cuticle, has been 

 drawn out of the tube of basement-membrane, as 

 far as the gland, where it begins to be contorted. 

 The cavity of the duct is seen dilating as it enters 

 the cuticle, and then stretching up to the surface 

 through the epidermic lamince. The deep surface 

 of the duct is continuous with the surface of the 

 cavities in which the papillae are lodged. Magn. 

 35 diameters. 



b. Duct at its entrance into the cuticle. More 

 highly magnified.] 



number of square inches of surface, in a man of ordinary stature, is about 

 2500; the total number of pores, therefore, may be about seven millions; 

 and the length of the perspiratory tubing would thus be 1,750,000 inches, or 

 145,833 feet, or 48,611 yards ; or nearly 28 miles. 



869. The Secretion of fluid by these Glands is continually taking place ; 

 but this fluid, being usually carried off in the form of vapour as fast as it is 

 separated, does not accumulate and become sensible. If, however, from the 

 increased amount of the secretion, or from the* condition of the surrounding 

 air, the whole fluid thus poured out should not evaporate, it accumulates in 



