merce.

In the course of the summer or autumn, the fly lays its eggs on a growing violet-stalk, and the young grubs, as soon as they are hatched, eat their way into the interior, where they find food and protection till the warm weather arrives. The ascending juices being interrupted by their operations, the stalk swells around them to a considerable thickness; but by this disfiguration of the plant, their food is only the more increased, and they are better secured against the cold. On the return of summer, they bore their way out of their vegetable prison, and make their escape in the adult shape of flies.

The violet, like most other plants, may be employed in medicine. It is deservedly a favorite in every rustic pharmacopeia. An excellent syrup is made from its flowers; its dried leaves furnish us with numerous useful decoctions and ointments; and an infusion of its seeds operates as a remedy for several severe diseases. Thus it is full of healing virtue, in addition to its other useful properties.

Now the violet is but a specimen of the innumerable wild flowers that adorn the exuberant lap of Nature, and pour forth their treasures to man, while they feed his eye with the purest delight. Were human labor wholly to cease in respect to flowers, and the garden and flower-bed henceforth to lie desolate, still would every sunny and shady nook teem with glowing and perfumed blossoms,still would the loneliest wilds be crowned

"With luxury of unexpected sweets,"

and exhibit the most delicate specimens of the beautiful, traced by His hand, who is Himself the perfection of beauty. Boundless are the vegetable stores with which the earth is strewn ; and their extent is only equalled by their utility and loveliness. They all proclaim a great and benevolent Creator :-the majestic oak and the lowly violet of the vale, utter one harmonious voice of praise. Our duty is to listen to that voice with joy, and add our own intelligent adoration.

J. D.

THE

ANIMAL

THIRD WEEK-FRIDAY.

STRUCTURE.-CELLULAR TEXTURE-MEM

BRANES, TENDONS, AND LIGAMENTS.

RESERVING to the subsequent seasons what yet remains to be said of the varieties of the vegetable creation, let us now turn our eye on the animal kingdoin. The functions of animated nature differ from those of vegetation, not merely in the higher energies of sentient beings, but in other circumstances of their condition, suited to their more exalted station in the scale of existence. Vegetables are fixed to a spot from which they derive their nutrition, and where their reproductive powers are called into action; and to these purposes alone, if we except their relation to the animal world, their structures are adapted.

But, besides the powers of nutrition and reproduction, the faculty of volition, and those of personal enjoyment and suffering, belong to animal life. The exercise of these qualities required a greater range of space; and accordingly, animated beings,-those of them at least in whom such powers are fully developed,-are not attached to a single spot, but are formed capable of locomotion. This change of condition rendered various corresponding changes necessary in their organization; and it is exceedingly edifying to observe the nature of these changes, as manifesting at once unity of purpose, and most skilful adaptation to circumstances, in the universal Creator.

The element," says Dr. Roget, in his Bridgewater Treatise, which we recognise without difficulty, as composing the greater portion of animal structures, is that which is known by the name of the cellular texture. Although bearing the same designation as the elementary material of the vegetable fabric, it differs widely from it in its structure and mechanical properties. It is not, like that of plants, composed of a union of vesicles, but is formed of a congeries of extremely thin laminæ, or plates,

variously connected together by fibres, and by other plates which cross them in different directions, leaving cavities or cells. These cells, or rather intervening spaces, communicate freely with one another, and, in fact, may be considered as one common cavity, subdivided, by an infinite number of partitions, into minute compartments. Hence the cellular texture is, throughout, readily permeable to fluids of all kinds, and retains these fluids in the same manner, and on the same principle, as a sponge." This texture is not only flexible in all directions, but highly elastic, and is thus admirably suited to the purposes of locomotion, to which the vegetable tissue could not be advantageously applied; as the nature of its formation, while it admits, indeed, of very considerable flexibility in the direction of its breadth, and also, to a certain extent, of elasticity and the power of extension, is yet comparatively rigid in other directions. The properties of flexion and extension, existing in the animal texture, are variously modified and adjusted, to suit the exigencies of the case. "When, for instance, different parts require to be moveable on each other, the cellular substance interposed between them, has its state of condensation adapted to the degree of motion required; that which connects the muscles, or surrounds the joints, and all other parts concerned in extensive action, has a loose texture, being formed of broad and extensible plates, with few lateral adhesions, and leaving large interstices; while, the more quiescent organs, the plates of the cellular substance, are thin and small, the fibres short and slender, and their intermixture closer and more condensed." The quality of elasticity, again, not only resists the displacement of parts, but, when displaced, causes them to possess a tendency to return to their natural position, and that in a degree, and to an extent, which is neither required nor possessed in the vegetable mechanism.

When it is necessary to interpose a barrier to the transmission of fluids, this is effected by membranes, which are merely "modifications of the same material, spread out into a continuous sheet, of a closer texture." These furnish strong coverings for the investment, the

support, and the protection of all the important organs of the body.

Such membranous textures are also employed in forming tubes for conducting fluids, which, in the higher classes of animals, traverse the body in innumerable canals, and which, when uniting into trunks, or subdividing into branches, are called vessels. The fluids contained in vessels are never stagnant, but are almost always carried forward in one constant direction. For preventing the retrograde motions of fluids passing along these canals, recourse is had to the beautiful contrivance of valves. The inner membrane of the vessel is employed to construct these valves; for which purpose, it is extended into a fold, having the shape of a crescent, and fixed, by its convex edge, to the sides of the vessel, while the other edge floats loosely in its cavity. Whenever the fluid is impelled in a direction contrary to its proper course, it raises the loose edge of the valve, which, being applied to the opposite side of the canal, effectually closes the passage. On the contrary, it presents no obstacle to the natural flow of the contents of the vessel, both edges. being then closely applied to the same side. Frequently two, or even three, valves are used at the same part, their edges being made to meet in the middle of the passage, like the floodgates or locks of a canal. Among the numberless instances of express contrivance, which are met with in the examination of the fabric of animals, there is perhaps none more striking and more palpable than this admirable mechanism of the valves.

To this general sketch of the fleshy and membranous structure of animals, I may add that of ligaments and tendons, some of which are elastic and extensible, while others resist extension with great force. The former, consisting of twisted fibres, are generally employed for the support of heavy parts, which require suspension, such as the necks of quadrupeds which stoop to graze ;

*

*This ligament is what butchers call the pax-wax. Dr. Paley is mistaken, when he says, that these elastic ligatures are peculiar to the necks of quadrupeds. They are frequently employed in the human frame. "The student," says Sir Charles Bell, "who hangs his head

the latter, which are most artificially contrived, by the interlacing and knotting together of fibres, are applied to the purposes of connexion, where motion is to be restrained. Nothing can be more remarkable than the ingenuity, if I may be allowed to use the expression, of these contrivances, and the adaptation of their mechanism to the purposes to which they are respectively applied. The precise degree of tension, of strength, of elasticity, or the contrary, which the function required, has been apportioned with the most perfect skill; and it is impossible to examine these structures with a scientific eye, and not acknowledge that there is a wisdom here, which art may imitate, but can never equal.

THIRD WEEK-SATURDAY.

THE ANIMAL STRUCTURE.-SECRETION-DIGESTION-AND THE CIRCULATION OF THE BLOOD.

THERE is another property of animal life, which, on account of its universal application, and its absolute necessity, seems to demand some notice in these preliminary sketches;—I mean the function of secretion. This capability of effecting chemical changes in the crude materials received into the body, I have already described as existing in vegetable life; but, in the animal frame, it is much more extensive and powerful. The food of plants is drawn directly from the soil in which their roots are placed, and the atmosphere with which they are surrounded, and consists of simple combinations of elementary bodies, which secretion converts into the various products that their wants require. From this process, the tree receives its leaves, its pith, and its woody fibres. Whatever is peculiar to the species is also derived from over his book, enjoys the advantage of this elastic support; so that it is strictly a matter comparative. We may trace it with increasing strength, from the ligament that sustains a man's head, to that which, like the spring of a steelyard, weighs against the immense head of the elephant." VIII.

II.

9