74 



THE SKIN. 



tubular coil, when unravelled, about ^L.th of an inch. The 

 entire length of the glandular tubing must, therefore, be not 

 less that 153,000 inches, or about two miles and a-half. 



Fig. 175. 



Fig. 175. (ERCOLANI.) Showing the arrangement of the glands and wool, a, Excre- 

 tory duct of a sweat-gland ; b, Oil or sebaceous gland ; c, Hair-follicle ; d, Hair-bulb. 

 Fig. 176. Hair-follicle from the interdigital canal of the sheep, showing the oil-glands. 



The sweat-glands are constantly discharging secretion in the 

 form of insensible perspiration, and it has been calculated 

 that a man thus loses nearly two pounds weight of fluid 

 daily. It has been estimated that a horse weighing 8 cwt. 

 loses, in 24 hours, about 14 Ibs. 5 oz. of fluid by the skin. 

 Milne Edwards has found that a Guinea pig loses as much 

 as the twelfth of the weight of its body in twenty-four hours 

 by cutaneous exhalation. 



