BIRD. 



451 



this wide setting of the tarsi, and not to any want of 

 firmness in the articulation of the toes, that the birds 

 owe their rolling' gait when they walk. The foot is 

 nearly a semicircle, or rather a semioctagon of un- 

 equal sides, of which the outer toe (which is generally 

 very long) and the back one form the largest diameter. 

 This is articulated upon the tarsus, intermediate be- 

 tween the directions of inward and forward, as may 

 be seen in the annexed cut of the foot of the gannet, 

 which, as one of the most active und best known 

 birds of the group, may be taken as the type, in as 

 far us the foot is concerned. 



Gannet. 



The birds which have this structure of foot are all 

 fishers, and most of them (the gannets especially) 

 dash down almost perpendicularly from great heights 

 upon their prey, and seize it with the bill. _ The gan- 

 net is curiously provided against any injurious effect 

 from these headlong plunges. On the breast and 

 throat of this bird there are three great air-cells 

 between the integuments and the muscles, the two 

 largest divided (but not shut out) from each other by 

 a perforated septum along the keel of the sternum, 

 and tied to the enveloping membrane of the muscles 

 by a number of small straps of membrane ; and the 

 smaller one anterior of the furcal bone, and not com- 

 municating with the other two, though all the three 

 have communications with the air-cells in the interior 

 of the bird. When the bird dashes down at a fish, 

 the air in those cells breaks its fall ; acts like a para- 

 chute in preventing it from going too deep ; probably 

 invigorates its vital system by the application of a 

 portion of air, condensed by the resistance and cool- 

 ing eifect of the water, to the coats of the arteries ; 

 mil, what is more to our present purpose, assists it in 

 recovering its position, in order that it may remount 

 the sky, after it has cither caught its prey or failed in 

 doing so. This quantity of air is of course condensed 

 by the collision ; but when that is over it expands 

 and raises the anterior part of the body, and at the 

 same time throws the centre of gravity further back- 

 wards, or more in a line with the feet. These at the 

 same time press downward with their curious webs, 

 both brought tinder the body by the position in which 

 the toes are articulated on the tarsi, and so heave the 

 body upward in the same manner, or at least upon 

 the same principle, that ordinary swimming feet impel 

 the body of a bird forward. Thus, what with the 

 action of the air, and what with that of the feet, the bird 

 is able to regain the wing without any difficulty. 



When the proper action of the foot is connected 

 with some action of the wings of the bird, as adapting 

 the foot for some particular kind of surface, or to 

 accomplish some other object in the general economy 

 of the creature, it always lessens the perfection 

 of the organ as a foot, whether for swimming or for 

 walking. 



Concentration upon one single part, or upon the 



smallest number of parts possible, is always the 

 structure of maximum action in nature. We find 

 it in the wing of the swift, in the foot of the ostrich, 

 in the feet of all the swifter running birds, and in the 

 more perfect swimmers ; for though these have the 

 back toe with a marginal lobe, which appears to 

 answer some purpose in the oblique motions of the 

 foot, just as the bastard wing appears to assist in the 

 oblique motions of the main one, though what the spe- 

 cific motion or assistance which this partially developed 

 part gives in the performance of it, can be found only 

 by a more nice and thorough analysis than has 

 hitherto been applied to the mechanics of animals. 



This delightful study is, indeed, as humbling to the 

 pride of human learning as it is gratifying to the 

 spirit of more lowly but more reverential inquiry ; 

 and the man who comes to it mailed and cuirassed all 

 over with the forms and the formulae of the schools, is 

 much in the same predicament as the young Israelite 

 when he put on the armour of the king to combat 

 with the giant Philistine he is encumbered and op- 

 pressed ; and if he would hope to conquer, he finds 

 that " the smooth stone from the brook" that which 

 nature affords to observation, must be the true weapon 

 of his warfare, and all his learning only " the sling," 

 by means of which it is sent to its destination with 

 the requisite force. 



And if they who weary their days under the load 

 of the armour, had not their eyes dimmed and dazzled 

 by its glitter, they would see that such must be the 

 case : that natural action the action of that which has 

 life must have a way of its own, according to which, 

 and only according to which, it can be studied. In 

 a machine of human contrivance, not only all the 

 parts, and the precise degree in which each part con- 

 tributes to the compound effect of the whole, can be 

 determined, but the motive power can also be esti- 

 mated with the greatest accuracy, and the whole can 

 be planned, and what it could or could not accomplish 

 known, before there is one peg of it in existence, and 

 though it never should exist. 



In the animal structure we can also examine all the 

 parts, and, comparing them with what they do in one 

 case, we can form an appropriate judgment of what 

 they can do in another. We can say, for instance, 

 of the action of a foot in swimming, that it is a 

 function" of certain bones, and muscles, and tendons, 

 and membranes, and other parts, all of which may be 

 eliminated by the knife of the dissector. But we do 

 not thus arrive at the specific action of the foot, either 

 in power or in mode, for that is also a " function " of 

 the energy of life in the animal ; and so far from being 

 able to express this energy in terms of any known 

 or measurable quantities, we have no expression at 

 all involving it, but that very compound action, the 

 principles of which we seek thus in vain to analyse. 



But even this, mortifying as it is to those who 

 labour to appear wise, is fraught with the same ad- 

 vantages and pleasure which are found everywhere 

 in nature. The animal cannot be wholly brought 

 into the closet, so as that the scientific recluse can 

 become fully acquainted with it there, at the sacrifice 

 of much of his health, usefulness, and pleasure. He 

 must go to field and flood, and see the creatures, 

 otherwise he may dream out the years of Methuselah 

 (if the canker of his seclusion shall not eat him up in 

 the twentieth part of that long period), without one 

 moment of awakening to reality and knowledge. 

 Thus, as it were, the coyness of nature is one of her 

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