SYSTEMATIC ANALYSIS OF TISSUES AND FLUIDS. 143 



565. PLANTS thrust their roots into the ground 

 and their branches and leaves into the air, and, basking 

 in the rays of the sun, gather from the air, water, and 

 earth the various elements that, under the influence and 

 power of the sun's rays during a long period of time, 

 they combine into indefinite compounds, possessed of the 

 power that has thus grown up in them. 



566. As COAL slumbering in the Earth contains heat 

 embodied, during ages past, in the growing plants of 

 which coal is the remains, so do the nutritious parts of 

 plants embody power derived from the sun during their 

 production, which power will come out again when their 

 decomposition takes place. The coal may lie for a day 

 or for ages the heat locked in it will appear when- 

 ever and wherever it returns to the form it had. So the 

 grain of wheat may remain a month or a year unchanged, 

 yet contains a latent power, the source of which was the 

 sun, that will be exhibited whenever decomposition 

 takes place. 



567. THE INFLUENCE OF THE SUN'S KAYS, acting 

 through the mechanism of plants, stores up power in 

 their nutritious parts. This power is not lost when they 

 are eaten, but follows the substances in which it exists 

 till they have become Tissues, and decompose, when it 

 again exhibits itself. 



568. THE SUBSTANCES FURNISHED BY PLANTS doubt- 

 less require some further preparation before they are 

 quite ready to become components of the Tissues ; and 

 it has been seen that they are subjected to the action of 

 secretions, and it may be to secretory processes in the 

 course of the Blood-circuit. 



560. THE BLOOD-CELLS are merely very simple 

 plants floating in the Blood ; the process of secretion, 

 which is the only office they can perform, being a vege- 

 tative or plant-like process. 



565. What said ? 566. What said of ? 567. What said of ? 568. What 

 said of ? 569. What are ? 



