CHAPTER XIX. 



THE INCOME AND EXPENDITURE OF THE 

 BODY. 



The Material Losses of the Body. All day long while 

 life lasts each of us is losing something from his Bod}. 

 The air breathed into the lungs becomes in them laden 

 with carbon dioxide and water vapor, which are carried off 

 with it when it is expired. The skin is as constantly giv- 

 ing off moisture, the total quantity in twenty-four hours 

 being a good deal, even when the amount passed out at any 

 one. time is so small as to be evaporated at once and so does 

 not collect as drops of visible perspiration. The kidneys 

 again are constantly at work separating water and certain \ 

 crystalline nitrogeneous bodies from the blood, along with ( 

 some mineral salts. The product of kidney activity, how- 

 ever, not being forthwith carried to the surface but to 

 a reservoir, in which it accumulates and which is only 

 emptied at intervals, the activity of those organs appears 

 at first sight intermittent. If to these losses we add cer- 

 tain other waste substances added to the undigested residue 

 of the food passed out from the alimentary canal, and the 

 loss of hairs and of dried cells from the surface of the skin, 

 it is clear that the total amount of matter removed from 

 the Body daily is considerable. The actual quantity varies 

 with the individual, with the work done, and with the 

 nature of the food eaten; but the following table gives 

 approximately that of the more important daily material 

 losses of an average man. 



