VITAL PRINCIPLE. 19 
the stays of a ship’s mast, preserve the trunk in its verti- 
cal position. 
In like manner, the Acorn-shells (Balani), when grow- 
ing on the firm, even surface of a plank or shell, present a 
regularity in the margin, and a narrowness of base, widely 
different from the irregular spreading bottom of the same 
species, when seated on the friable and uneven surface of a 
rock. In the former case, the shells are frequently of a 
cylindrical form; while, in the latter, they are uniformly 
approaching to conical. In a variety of other cases, which 
might be brought forward from the Vegetable and Animal 
Kingdom, where the obstacles are as various as the beings 
which encounter th2m, we perceive a unity of purpose, and 
a striking resemblance among the means employed for its 
attainment. 
This instinctive principle, while it regulates the means to 
be employed in obtaining food and avoiding obstacles, like- 
wise repairs the injuries to which organized bodies are lia- 
ble. ; 
C. Repairs Injuries.—Plants are exposed to a greater 
variety of accidents than animals. Destitute of the loco- 
motive faculty, they neither can fight for victory, nor re- 
treat for safety. In some cases, it is true, they close their 
flowers, or hang down their heads, to defend the unripe 
pollen from the heat, the wind, or the dew. But though 
they do not in general possess the means of avoiding inju- 
ries, they are abundantly provided with the power to re- 
pair them. Thus, when the branch of a tree is torn from 
the stem, the bark accumulates around the wound, and, in 
time, covers the offensive scar. The plants with which we 
form our hedges, still live, though sadly mutilated by the 
shears, and push forth afresh those branches and leaves 
necessary to the continuance of their being. The utility, 
indeed, of many of our culinary vegetables, such as parsley, 
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