A stable should not only be roomy, so as to afford the horses a comfortable abode, but should also be fairly lofty, in order that it may contain a comparatively large volume of air; because in that case, it will be easier to maintain the purity of the air inside, without the necessity of creating a draught, than it would be if the cubic content of the building were less. It is evident that the smaller the quantity of air in a stable, the quicker will it have to be renewed in order to preserve a healthy standard of purity. Supposing that a stall was 6 ft. wide, 10 ft. long, and 10 ft. high, it would contain 600 cubic feet of space. To this we might add two-thirds more for passages, etc, and would thus arrive at a total of 1,000 cubic feet, which would probably be a fair minimum. I do not think that less space than that would afford a healthy place of residence for horses; and even then, every precaution should be taken to obtain free ventilation. If a box consisted of a single room or small house with only one door, 1,500 cubic feet (say 12 ft. x 12 ft. X 10 1/2 ft.) would be a reasonable average; although the addition of a couple of feet to the height would be an improvement. I do not think that 2,500 cubic feet (say 14 ft. X 15 ft. x 12 ft.) need be exceeded, even for high-class racehorses. It goes almost without saying, that the more confined the situation, the greater should be the cubic content.