190 ANATOMY AND PHYSIOLOGY. 



hand there exists a length of tube equal to 882 inches, or 73J feet. 

 The number in other parts of the skin is sometimes greater, but 

 generally less than this ; and according to Mr. Wilson, about 2800 

 inches may be taken as the average number of pores in each square 

 inch throughout the body. Now the number of square inches of 

 surface, in a man of ordinary stature, is about 2500 ; the number 

 of pores, therefore, is seven millions ; and the number of inches 

 of perspiratory tubing would thus be 1,750,000 ; or 145,833 feet ; 

 or 48,611 yards ; or nearly 28 miles. 



The Anatomy of the Skin. 



1. The epidermis, showing the oblique laminae of which it is composed, and the disposition of the 

 ridges upon its surface. 2. The rete mucosum or deep layer of the epidermis. 3. Two of the 

 quadrilateral papillary clumps, such as are seen in the palm of the hand or sole of the foot ; they 

 are composed of minute conical papillae. 4, The deep layer of the cutis, the corium. 5. Adipose 

 cells. 6. A sudoriparous gland with its spiral duct, such as is seen in the palm of the hand or sole 

 of the foot. 7. Another sudoriparous gland with a straighter duct, such as is seen in the scalp. 

 8. Two hairs from the scalp, enclosed in their follicles ; their relative depth in the skin is pre- 

 served. 9. A pair of sebaceous glands, opening by short ducts into the follicle of the hair. 



From this extensive system of glands, a secretion of watery fluid 

 is continually taking place ; and a considerable amount of solid 

 matter also is drawn off by the epithelium-cells that line the tubes. 

 Under ordinary circumstances, the fluid is carried off in the state of 

 vapor, forming the insensible perspiration ; and it is only when its 

 amount is considerably increased, or when the surrounding air is 

 already so loaded with moisture as to be incapable of receiving 

 more, that the fluid remains in the form of sensible perspiration upon 

 the surface of the skin. It is difficult to estimate the proportion of 

 solid matter contained in this secretion ; partly on account of the 



