XI PHENOMENA OF ORGANIC NATURE 311 



term technically its Morphology), I must now turn 

 to another aspect. A horse is not a mere dead 

 structure : it is an active, living, working machine. 

 Hitherto we have, as it were, been looking at a 

 steam-engine with the fires out, and nothing in the 

 boiler; but the body of the living animal is a 

 beautifully-formed active machine, and every part 

 has its different work to do in the working of that 

 machine, which is what we call its life. The 

 horse, if you see him after his day's work is done, 

 is cropping the grass in the fields, as it may be, or 

 munching the oats in his stable. What is he 

 doing ? His jaws are working as a mill and a 

 very complex mill too grinding the corn, or 

 crushing the grass to a pulp. As soon as that 

 operation has taken place, the food is passed down 

 to the stomach, and there it is mixed with the 

 chemical fluid called the gastric juice, a substance 

 which has the peculiar property of making soluble 

 and dissolving out the nutritious matter in the 

 grass, and leaving behind those parts which are 

 not nutritious ; so that you have, first, the mill, 

 then a sort of chemical digester ; and then the 

 food, thus partially dissolved, is carried back 

 by the muscular contractions of the intestines into 

 the hinder parts of the body, while the soluble 

 portions are taken up into the blood. The blood 

 is contained in a vast system of pipes, spreading 

 through the whole body, connected with a force- 

 pump, the heart, which, by its position and by 



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