200. Leeches vary considerably in size; and their blood-extracting capacity is, as a general rule, in proportion to their size. It has been found that small Leeches will abstract two and a half times, small middle-sized four times, large middle-sized five and a half times, and large ones nearly six times their own weight of blood. Hence, to abstract a certain quantity of blood, a very much larger number of small Leeches is required than of large ones. The middle-sized Leech, from 1½ to 2 inches in length when at rest, is in all cases preferable. The very small leeches so commonly supplied in India are objectionable on account of the number of bites, the length of time required in their application, and the indefinite small oozing of blood which follows their application, and the difficulty in arresting the flow by pressure. On the other hand, the very large Leech is objectionable, from the large gaping wound left by its bite, which often results in an ugly scar; this applies with peculiar force to childhood and infancy. 201. Where only one or two Leeches have to be applied, they may be taken in the hand and held to the spot where it is desired they should bite, but this is a long and tedious process; when several are to be applied, they should be put in a wineglass and thus held to the surface till they have all taken. 202. In order to make Leeches bite readily, thoroughly cleanse the skin with soap and water, and then dry it; this is particularly necessary if a liniment has been previously employed. If they will not bite, one or more of the following plans may be tried: 1. Remove them from the water and keep them for ten minutes in a dry, warm cloth. 2. Smear the skin with cream or sugared milk. 3. Apply a small mustard poultice over the spot. After carefully cleansing with hot water, apply the Leeches. Not only will they bite more readily, but the flow of blood will be far greater than it otherwise would be. 4. Make a small puncture or scratch on the skin, and smear the blood over the surface; this often succeeds when everything else fails. It should also be remembered that the fumes of sulphur, vinegar, or tobacco in a room, will often prevent Leeches from biting at all. 203. To make Leeches bite on particular spots, take a piece of blotting-paper and make in it as many small holes as there are Leeches, the holes corresponding with the spots on which it is desired to apply the Leeches; they are then to be covered over with a wineglass or tumbler; the Leeches, finding themselves on a rough surface, creep about till they come to the holes in the paper, when they instantly bite the exposed points of the skin; the blotting-paper is easily removed by being moistened. 204. When Leeches will not drop off naturally, which they generally do in about fifteen minutes or less, or if you wish to remove them, sprinkle them with a little salt or vinegar, or touch them with a piece of onion; the last is an old Bengali practice.