404 BIOLOGY FOR BEGINNERS 



wastes which it contains are of such character that if incompletely 

 removed, very serious diseases are sure to result. 



Exposure to cold, drinking large quantities of water, and excess 

 of proteid food all tend to increase the amount of urine. As some 

 of the waste matters are not very soluble, it is a good thing to 



* 



FIG. 131. Section perpendicularly through skin, a, epidermis; b, pigmentary 

 layer of epidermis; c, papillary layer of dermis; d, dermis or true skin; e, fatty 

 tissue; /, g, h, sweat glands and duct; i, k, hair with its follicle and papilla; 

 I, sebaceous gland. (After Brubaker.) From Kellogg. 



drink plenty of water to keep the kidneys well washed out. As a 

 rule we drink too little rather than too much. 



The Lungs. The lungs are used as organs of excretion as well 

 as for the supply of oxygen, their wastes being carbon dioxide 

 mainly, together with considerable water and very little nitrog- 

 enous compounds. 



