THE LAW OF SERIES. 133 



Let us also remark in the preliminaries, that if the substances of 

 the external world were not inherently adapted for our sustenance, 

 the possibility of any series of changes harmonizing them with our 

 physical system, would be cut off; so that in the very fact of di- 

 gestion we find a co-ordained fitness between man and nature. This 

 we detect in all things the more and the better we look for it. It 

 is a well of truth to draw upon in the sciences, and especially in 

 human physiology. 



We have said that organizations depend for growth and mainte- 

 nance upon materials extraneous to themselves, and this is equally 

 true of the vegetable as of the animal kingdom. There is, however, 

 a difference between the methods of nutrition in the two cases. The 

 plant or tree is fixed by its roots into the soil, and imbibes at their 

 extremities the nutritious juices; it is imprisoned in a particular 

 spot, and its supplies depend upon the fertility of a very limited 

 area ; although by its leaves it extends into the movable atmosphere, 

 and at the summit of its powers begins to take advantage of the 

 new principle of locomotion. In the animal, on the other hand, 

 motion is the pedestal of life ; the pillars which support it are en- 

 gines of movement, and the ground under it is fluid ; its roots also 

 are turned inwards, collected and associated, and constitute reposi- 

 tories or stomachs, into which alimentary substances are carried by 

 proper animal actions. The range and freedom of animal exist- 

 ence immensely excel the strait security of the lower nature; the 

 precarious income of life is far better than the small certainties of 

 vegetation. Thus, while the stately tree subsists on a few square 

 yards of earth, the animal which it shades, and the bird that lodges 

 in its branches, choose their food from wide districts, and are only 

 confined by the barriers of nature, as the shores of the ocean, or 

 the limits of the climate. Moreover, the vegetable, with few ex- 

 ceptions, draws its sap from the underground — from the dark scurf 

 of the mineral kingdom; whereas, the animal takes its nutrient 

 juices from among the children of air, light, and motion; from the 

 succulent tops and fruits of nature ; from the results of an elaborate 

 previous digestion in the bosom of the earth, the plant, or even the 

 animal frame itself. 



Much more are these superiorities true of man physically, or 

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