PROBLEM <J, 



HoiD the Body Gets Rid of Wastes 230 



ous climates, or at different seasons of 

 the year, this is most amazing. Our mouth 

 temperature is about 98.6° F whether we 

 are out in a blizzard or sitting next to the 

 radiator or stove indoors, whether we 

 live at the north pole or at the equator. 



The process of oxidation releases heat 

 energy in the body. As more oxidation 

 goes on our temperature would tend to 

 rise. But the skin normally operates so 

 that as the temperature tends to rise it 

 is brought down. On the other hand 

 when there is less oxidation this activity 

 of the skin becomes less. The skin regu- 

 lates temperature in several ways; much 

 of it is done by the sweat glands. 



The sweat glands. If you examine your 

 skin with a magnifv^ing glass you will 

 find it closely dotted with pores. Many 

 of these are the openings of microscopic 

 sweat glands sunk down into your skin. 

 Water leaves them all the time. You can 

 test this by placing a close-fitting, clean, 

 dry vial over the end of one of your 



-J*l|PiPI'-^ 



Fig. 235 The branched tubes which carry urine 

 from the outer portion of a sheep^s kidney to 

 the kidney cavity, (ward's natural science 



ESTABLISHMENT, INC.) 



The skin is also an important organ. 

 The skin is an organ of excretion; it ex- 

 cretes water and small amounts of salts. 

 But this is not what makes it important 

 to the working cells. Its importance lies 

 in the fact that it is active in regulating 

 the body temperature. Protoplasm is a 

 sensitive, highly complex substance. If 

 conditions are varied beyond compara- 

 tively small limits, the protoplasm of your 

 body cells will cease to function nor- 

 mally. The skin covering the whole 

 body, under normal conditions keeps the 

 temperature of your cells almost uni- 

 form. Do Exercise 2 to see whether the 

 body temperature is kept uniform. When 

 you consider the extremes of temperature 

 to which many of us are exposed in vari- 



fingers. 



Each sweat gland consists of a long, 

 narrow tube which is coiled up at its 

 lower end. Around this coiled part is a 

 network of capillaries (Fig. 237). The 

 gland cells receive large quantities of 

 water and a small amount of various salts 

 from the plasma flowing through the 

 capillaries. These wastes diffuse into the 

 gland cavity as sweat. Thus the cavity 

 and duct of each gland become filled 

 with sweat. This overflows onto the skin 

 from each of the many glands. The salts 

 contained in the sweat remain on the 

 skin while the water evaporates, as you 

 can show if you do Exercise 3. 



The secreting of sweat is a continuous 

 process. Under normal conditions one 



