WHKELS OF LIFE. 53 



chemists, aud mechanics, have all learned much by observing 

 the work accomplished, but the a])]est physiologist cannot tell us 

 what is life, thougli he can give us a thousand proofs tliat 

 stagnation is death : the chemist cannot tell us how the oxygen 

 and carbon combine so as to maintain heat with such unerring 

 regularity in any climate ; the mechanic cannot discover how 

 a fluid so thick as blood is passed so rapidly through tubes too 

 fine to pass the purest watei', nor can he show us where the 

 motive power originates. The most elaborate, complete, and 

 delicate machine ever constructed by the skill of man, is a 

 clumsy, bungling, wasteful piece of mechanism compared 

 to the organisation that circulates, warms, and invigorates tlie 

 blood of the horse. 



105. — As it is a circle, without beginning or end, we may 

 with almost equal propriety take it up at any part. If our 

 review of the process could be more lengthy and complete, it 

 would perhaps be most natural to begin where the chyle, selected 

 from the food by the lacteals, is first introduced into the returning 

 stream of venous blood ; but as we must confine our examination 

 of the process to what is strictly necessary to get a rough 

 understanding of the subject we will begin at the heart, at the 

 great double force pump which appears to keep all in motion. 



1 06. — To the right side of the heart comes a stream of dark 

 fluid, composed of blood, that has gone the round of the 

 system, and of newly made chyle, selected and extracted by very 

 fine lacteals from the food passing through the bowels. This 

 mixture is immediately pumped out of the heart into the lungs 

 to be warmed, purified, and supplied with new oxygen. Tt 

 there gets rid of its load of poisonous carbonic acid gas, and is 

 changed from a dull dark to a bright red colour. How is all 

 this done in a few seconds ? The lungs are a beautiful sight 

 under the microscope, and would be far more so if it were possible 

 to see them at work. They contain millions of cells, too minute 

 to be seen by the eye, yet each cell receives its particle -of blood 

 or its particle of air, and without confusing them together, 

 allows the air to get near enough to the blood to give it oxygen 

 and to take away carbonic acid gas, to burn up waste material 



