V. "But, as I gather you would prefer, Axius, I will speak of that kind of _ornithon_ which is established for profit, whence, but not where, fat thrushes are served. "For this purpose is built a dome, in the form of a peristyle, with a roof over it and enclosed with netting, sufficiently large to accommodate several thousand thrushes[168] and blackbirds; indeed, some also include other kinds of birds, such as ortolans and quail, which sell for a good price when fat. Into this enclosure water should be conducted through a conduit and so disposed as to wind through the aviary in channels narrow enough to be cleaned easily (for if the water spreads out it is quickly polluted and rendered unfit to drink) and draining like a running stream to find its vent through another conduit, so that the birds may not be exposed to the risk of mud. The door should be low and narrow and well balanced on its hinges like the doors they have in the amphitheatres where bulls are fought: few windows and so placed that the birds cannot see trees and wild birds without, for that makes the prisoners pine and grow thin. The place should have only so much light as may be necessary to enable the birds to see where they are to perch and to eat and drink. The doors and the windows should be lightly stuccoed round about to keep out rats and other such vermin. "Around the wall of the building on the inside are fastened many perches where the birds can sit, and another such convenience should be contrived from poles set on the ground and leaning against the walls and tied together with other poles fastened transversely at regular intervals, thus giving the appearance of the rising degrees of a theatre. Down on the ground near the drinking water you should place the birds' food, which usually consists of little balls of a paste made out of figs and corn meal: but for twenty days before you intend to market your thrushes it is customary to feed them more heavily, both by giving them more food and that chiefly of finer meal. "In this enclosure there should also be cages with wooden floors which may serve the birds as resting places supplementing the perches. "Next to the aviary should be contrived a smaller structure, called the _seclusorium_, in which the keeper may array the birds found dead, to render an account of them to his master, and where he may drive the birds which are ready for market from the larger aviary: and to this end this smaller room is connected with the main cage by a large door and has more light: and there, when he has collected the number he wishes to market, the keeper kills them, which is done secretly, lest the others might despond at the sight and themselves die before they are ready for market.