CHAPTER XVI.

COMPENSATION.

COMPENSATION is a species of relation. It is relation when the defects of one part, or of one organ, are supplied by the structure of another part, or of another organ. Thus,

I. The short unbending neck of the elephant is comlateral rows of filaments; and which float loosely in the general cavity of the body, attached only at their termination, where they open into the alimentary canal." See Dr. Roget's Bridgewater Treatise, vol. ii. p. 208.

In the mantis religiosa, which is purely a carnivorous insect, the whole canal is more simple, it is perfectly straight; commencing by an esophagus of great length, which is preceded by a gizzard, hepatic vessels, and a digesting stomach, it is terminated by a short intestinal tube.

Of the perceptions of the lower animals and of the laws which they obey, our knowledge must, of necessity, be extremely imperfect, since it must be derived from a comparison with the results of our own sensitive powers, which may differ very essentially from those of the subjects of our observation. The same kind of organ which, in ourselves, convey certain definite feelings, may, when modified in other animals, be the source of very different kinds of sensations and perceptions, of which our minds have not the power to form any adequate conception. Many of the qualities of surrounding bodies, which escape our more obtuse senses, may be distinctly perceived, in all their gradations, by particular tribes of animals, furnished with more delicate organs. Many quadrupeds and birds possess powers of vision incomparably more extensive than our own; in acuteness of hearing, we are excelled by a great number of animals; and in delicacy of taste and smell, there are few quadrupeds who do not far surpass us. The organ of smell, in particular, is often spread over a vast extent of surface, in a cavity occupying the greatest part of the head; so that the perceptions of this sense must be infinitely diversified.

The perceptive powers of insects must embrace a very different, and, in many respects, a more extended sphere than our own. These animals manifest by their actions, that they perceive and anticipate atmospheric changes, of which our senses give no information. But neither our thermometers, nor our electroscopes, nor hygrometers, nor our galvanometers, however skilfully devised or elaborately constructed, can vie in delicacy and perfection with that refined apparatus of the senses which nature has bestowed on even the minutest insect. See Dr. Roget's Bridgewater Treatise, vol. ii. p. 571.

pensated by the length and flexibility of his proboscis. He could not have reached the ground without it; or, if it be supposed that he might have fed upon the fruit, leaves, or branches of trees, how was he to drink? Should it be asked, Why is the elephant's neck so short? it may be answered, that the weight of a head so heavy could not have been supported at the end of a longer lever. To a form, therefore, in some respects necessary, but in some respects also inadequate to the occasions of the animal, a supplement is added, which exactly makes up the deficiency under which he laboured.

If it be suggested that this proboscis may have been produced, in a long course of generations, by the constant endeavour of the elephant to thrust out his nose, (which is the general hypothesis by which it has lately been attempted to account for the forms of animated nature,) I would ask, How was the animal to subsist in the mean time, during the process, until this prolongation of snout were completed? What was to become of the individual, whilst the species was perfecting?

Our business at present is, simply to point out the relation which this organ bears to the peculiar figure of the animal to which it belongs. And herein all things correspond. The necessity of the elephant's proboscis arises from the shortness of his neck; the shortness of the neck is rendered necessary by the weight of the head. Were we to enter into an examination of the structure and anatomy of the proboscis itself, we should see in it one of the most curious of all examples of animal mechanism.* The disposition of the ringlets

*Tab. XXX. Fig. 2. The head of the elephant. Fig. 3 and 4, the digitated extremity of the proboscis.

Fig. 5. A transverse section of the proboscis, showing, a, a, the two tubes or nostrils. Between the external integuments and the tubes are

and fibres, for the purpose, first, of forming a long cartilaginous pipe; secondly, of contracting and lengthening that pipe; thirdly, of turning it in every direction at the will of the animal; with the superaddition at the end of a fleshy production, of about the length and thickness of a finger, and performing the office of a finger, so as to pick up a straw from the ground; these properties of the same organ, taken together, exhibit a specimen, not only of design, (which is attested by the advantage,) but of consummate art, and, as I may say, of elaborate preparation, in accomplishing that design.

II. The hook in the wing of a bat is strictly a mechanical, and also a compensating contrivance.*

At

two sets of small muscles; an inner one running in a transverse, and an outward one in a longitudinal direction, b, b, the transverse faciculi of muscles, some of which run across the proboscis, others in a radiated, and some in an oblique direction; c, c, the radiated, and d, d, the oblique fibres, approximate the skin and the tubes, without contracting the cavity of the latter. The others, which pass across the proboscis, contract both the surface of the organ, and the canals it contains; they can, at the same time, elongate the whole or a part of it: e, e, the longitudinal faciculi, forming four large muscles, which occupy all the exterior of the organ. These are divided by tendinous intersections, and take their origin from the bones of the face. They give that extraordinary power which the animal possesses of moving the proboscis in every direction.

The tubes are prolongations of the external openings of the nose, and are lined by a strong tendinous membrane. They are separated from each other, and are both surrounded by adipose substance, which also is extended between the muscles we have already described. The outer part is covered by a tendinous expansion, and the common skin. The proboscis serves to pump up the drink which the animal takes in, as well as for smelling, breathing, and the various offices of feeding itself, etc. which most persons who have seen the animal must have witnessed with admiration.

Fig. 6. The extended wings of the bat. Osteologically considered they are hands, the bony stretchers of the membrane being the finger bones extremely elongated: a, a, the thumb, is short, and armed with a hooked nail, which these animals make use of to hang by, and to creep. The hind feet are weak, and have toes of equal length, armed also with

the angle of its wing there is a bent claw, exactly in the form of a hook, by which the bat attaches itself to the sides of rocks, caves, and buildings, laying hold of crevices, joinings, chinks, and roughnesses. It hooks itself by this claw; remains suspended by this hold; takes its flight from this position: which operations compensate for the decrepitude of its legs and feet. Without her hook, the bat would be the most helpless of all animals. She can neither run upon her feet, nor raise herself from the ground. These inabilities are made up to her by the contrivance in her wing: and in placing a claw on that part, the Creator has deviated from the analogy observed in winged animals. A singular defect required a singular substitute.

III. The crane kind are to live and seek their food amongst the waters; yet, having no web-foot, are incapable of swimming. To make up for this deficiency, they are furnished with long legs for wading, or long bills for groping; or usually with both.* This is compensation. But I think the true reflection upon the present instance is, how every part of nature is tenanted by appropriate inhabitants. Not only is the surface of deep waters peopled by numerous tribes of birds that swim, but marshes and shallow pools are furnished with hardly less numerous tribes of birds that wade.

hooked nails; the membrane, constituting the wing, is continued from the feet to the tail.

* These are waders, a class of birds very numerous, and differing in interior and exterior conformation, but agreeing in this one particular, viz. that they are invariably bare of feathers to midway above the knees; by which peculiarity of structure they can, without inconvenience, wade in shallow water in search of food, which, for the most part, consists of fish, small aquatic animals, roots, and seeds.

In the ostrich and emu, which are unable to fly, the compensation is muscular and powerful limbs; so that their speed is equal to the swiftest horse.

us.

IV. The common parrot has, in the structure of its beak, both an inconveniency, and a compensation for it. When I speak of an inconveniency, I have a view to a dilemma which frequently occurs in the works of nature, viz. that the peculiarity of structure by which an organ is made to answer one purpose, necessarily unfits it for some other purpose. This is the case before The upper bill of the parrot is so much hooked, and so much overlaps the lower, that if, as in other birds, the lower chap alone had motion, the bird could scarcely gape wide enough to receive its food: yet this hook and overlapping of the bill could not be spared, for it forms the very instrument by which the bird climbs; to say nothing of the use which it makes of it in breaking nuts and the hard substances upon which it feeds. How, therefore, has nature provided for the opening of this occluded mouth? By making the upper chap moveable,* as well as the lower. In most birds, the upper chap is connected, and makes but one piece with the skull; but in the parrot, the upper chap is joined to the bone of the head by a strong membrane placed on each side of it, which lifts and depresses it at pleasure.

V. The spider's web is a compensating contrivance. The spider lives upon flies, without wings to pursue them; a case, one would have thought, of great difficulty, yet provided for, and provided for by a resource which no stratagem, no effort of the animal, could have produced, had not both its external and internal structure been specifically adapted to the operation.

* Tab. XXX. Fig. 7. The upper mandible of the parrot, which is articuculated with the cranium by an elastic ligament, admitting of a considerable degree of motion.