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ing under shelter of the larger structure, either immediately below or to leeward. In winter, however, when the rooks do not come to the rookery, the sparrows, as we have remarked, are not so ceremonious in keeping their distance, thinking themselves at liberty to roost in the warmest nests they can select. In the rookery at Lee we have observed them, throughout the winter, assembling every night at sunset, squabbling together for nearly an hour, as if to settle their individual claims to particular nests belonging to the absent rooks*.

A sociality of a similar kind is mentioned by Wilson, as sometimes occurring among the purplegrakles and the fish-hawks of America. The nest of the fish-hawk (Pandion haliætus, SAVIGNY) is very large, being from three to four feet in breadth, and from four to five feet high, and composed externally, as we have already described, of large sticks or faggots. Among the interstices of this structure, sometimes three or four pairs of the crow-blackbirds (Quiscalus versicolor, VIEILLOT) will construct their nests, while the hawk is sitting or hatching above; and during incubation they seem to live in the greatest harmony, mutually watching and protecting each other's property from depredators t." This," says Wilson,

I have had many opportunities of witnessing. The grakles, or crow-blackbirds, are permitted by the fish-hawk to build their nests among the interstices of the sticks of which his own is constructed, several pairs of grakles taking up their abode there, like humble vassals around the castle of their chief, laying, hatching their young, and living together in mutual harmony. I have found no less than four of these nests clustered around the sides of the former, and a fifth fixed on the nearest branch of the adjoinWilson, Amer. Ornith. iii. 48.

* J, R.

ing tree, as if the proprietor of this last, unable to find an unoccupied corner on the premises, had been anxious to share, as much as possible, the company and protection of this generous bird*.'

The crow-blackbird (Quiscalus versicolor) furnishes a proof, among many others of the same kind, that its parasite habits are not original, but acquired; for, like our sparrows in a rookery, it is only occasionally that it nestles in the eyries of the fish-hawks. Its habits, indeed, seem to be very analogous to those of the rook, being equally omnivorous, at one time making prey of grubs, worms, and caterpillars, and at another proving destructive to corn and pulse. They are also very social, and when the business of feeding is over for the day, they assemble towards evening at the nearest group of cedar and pine-trees to roost, making a continual chattering as they fly along. "On the tallest of these trees," says Wilson, "they generally build their nests in company, about the beginning or middle of April, sometimes ten or fifteen nests being on the same tree. One of these nests, taken from a high pine-tree, is now before me, It measures full five inches in diameter within, and four in depth; is composed outwardly of mud, mixed with fine bent and horsehair. The trees where these birds build are often at no great distance from the farm-house, and overlook the plantations. From this they issue in all directions, and with as much confidence, to make their daily depredations among the surrounding fields, as if the whole were intended for their use alonet."

Those who are fond of harbouring birds near their habitations, take advantage of these parasite propensities of some species, by fixing conveniences for them to nestle in, about houses and gardens. Belon‡ * Wilson, Amer. Ornith. v. 22. + Ibid. iii. 45. Oiseaux, p. 326.

tells us, that in certain provinces of France, it is customary, in this way, to hang pots in the tops of trees which are haunted by thrushes; and these birds, finding convenient sheltered nests, seldom fail to lay their eggs in them, to hatch and rear their young. This plan, which, Aldrovand says, is unknown in Germany (nor is it, we believe, practised in Britain), contributes doubly to the multiplication of the species, for it both preserves the brood, and, by saving part of the time spent in building nests, it enables the birds to make two hatches a-year.

Buffon thinks this is a modern improvement upon the ancient Roman method of breeding thrushes for the table in voleries, of which Varro and Columella have left curious details. Each of these voleries contained many thousand thrushes and blackbirds, besides other birds excellent for eating, such as ortolans and quails. So numerous were those voleries in the vicinity of Rome, and in the territory of the Sabines, that the dung of the thrushes was employed to manure the lands, and, what is remarkable, to fatten oxen and hogs*. These thrushes had little liberty in their prisons, for they were never suffered to go abroad, and they laid no eggs; but as they were supplied with abundance of choice food, they fattened to the great profit of the proprietor. Each fat thrush, except at the time of migration, sold for three denarii, equal to about two shillings sterling; and on the occasion of a triumph or public festival, this sort of trade yielded a profit of twelve hundred per cent.† The voleries were a kind of vaulted courts, the inside furnished with a number of roosts. The door was very low; the windows were few, and placed in such a manner as to prevent the prisoners from seeing the fields, * Varo, de Re Rustica, i. 31. † Columella, de Re Rustica, viii. 10.

dency is to increased action. The growth of the body depends on this. The functions being all in an active state, a large quantity of blood is formed, from which the materials are supplied that increase the body and make up for the daily waste going on. This addition of new matter and the force of the circulation distend the different parts and add to their bulk. The addition of new matter, after some time, and the degree to which the extension has been carried impede the further continuance of the process, and the power of the arteries becomes so balanced with reference to the condition of the system as to cause its present state to continue. The balance, however, is soon destroyed by the diminished action; and the veins being more easily distended than the arteries, and having experienced less alteration in their texture, while they also partake less of vital action, the blood is more disposed to accumulate in them*.

This principle may be made still more plain by saying, that as age advances the fine hair-like bloodvessels, which branch off in every direction through the body, and more particularly through the skin and near the surface, become obstructed and imperforate, and consequently the skin and the other parts to which they run, not being supplied with their nourishment of fresh blood, shrink and wither; the internal parts becoming gradually more stiff and hard, and the skin first sallow and then dry and wrinkled. In such cases, when the smaller blood-vessels are obliterated, the larger ones swell with blood which cannot get vent, and this is the reason why we see old people's veins swell, as on the back part of the hands or feet.

Insects, though they have no circulating blood like the larger animals, furnish an analogical corro

* Cullen's Physiology, p. 249.

boration of the same views, for their parts soon becoming rigid and dry, old age comes rapidly upon them; few of them in their adult state living more than a few days or weeks, and some not many hours.

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Fishes," again, to use the words of Smellie, "whose bones are more cartilaginous than those of men and quadrupeds, are long of acquiring their utmost growth, and many of them live to great ages. Gesner gives an instance of a carp in Germany, which he knew to be one hundred years old. Buffon informs us that, in Count Maurepa's ponds he had seen carps of one hundred and fifty years of age, and that the fact was attested in the most satisfactory manner. He even mentions one which he supposed to be two hundred years old*. The element in which fishes live is more uniform, and less subject to accidental changes than the air of our atmosphere. Their bones, which are more of a cartilaginous nature than those of land animals, admit of indefinite extension; of course, their bodies, instead of suffering the rigidity of age at an early period, which is the natural cause of death, continue to grow much longer than those of most land animals †.”

It is a very prevalent notion that in what is termed and supposed to be a state of nature, diseases (assumed to be wholly caused by artificial living) do not occur; and it is accordingly maintained that wild animals, from living in this state of nature, are exempted from disease. But in opposition to this doctrine many strong facts might be adduced. We lately caught a mouse, which was in the last stage of malignant erysipelas, which carried it off in a few

* De Piscibus, p. 312. † Phil. of Nat. Hist. ii. 418, 8vo edit. See Abernethy, Physiol. Lectures, and Rush's Medical Observations.

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