NUTRITION. Ill 



is the principal ingredient in charcoal ; it is the predomi- 

 nant element in vegetable substances. 



240. All these elements are found in the blood. But they 

 are not all found in every tissue of the animal body. 

 There is no lime in the brain, no sulphur in the muscles, 

 and no nitrogen in the fat. Yet, with few exceptions, all the 

 various parts and organs are mainly composed of the same 

 elementary atoms carbon, oxygen, hydrogen, and nitro- 

 gen. The difference of these organs is owing, not to the 

 difference of their component" elements, but to their different 

 combination or arrangement. Combined in one proportion, 

 they form tendon ; in another, they form muscle ; in 

 another, potato, tea, coffee. The same elements in various 

 proportions, and with some ashes, form flesh, peas, beans, 

 oats ; and, with some sulphur, they form* hair, bone, nails, 

 and cheese. The blood is the grand storehouse which sup- 

 plies all these, in their due proportion, to every organ and 

 texture. 



241. The arteries carry this, blood to all the parts of the 

 body ; every point, however minute, receives its supply 

 through these tubes. The transformation of the blood into 

 flesh, or the separation of such elements from this fluid as 

 will compose the kind of flesh that is needed, is done in the 

 minute extremities of the arteries, or the capillaries, which 

 stand between the arteries and the veins. This work of nu- 

 trition is done with unerring precision in health ; just the 

 requisite proportions of carbon, oxygen, and hydrogen, and 

 of the other elements, are measured out ; and flesh of the 

 proper kinds is formed, each in jts appropriate place ; and 

 thus the body increas.es in size and stature. 



242. All additions to the weight of the body, the growth 

 during early years, and the increase of flesh at any time, 

 create a certain demand upon the blood for nutrition ; but 

 the changes of particles, during the whole of life, create 

 a much greater demand upon the blood for new atoms. 

 After we have reached our fulness of stature v in ordinary 

 health, we eat and drink three to four or more pounds of 



