Leeching and cupping each had their advocates. The major advantage of the leech over the cup was that the leech could be employed on almost any part of the anatomy, including around the eyes, in the mouth, the anus, and the vagina. In fact, leeching the internal membranes enjoyed quite a vogue in the early nineteenth century. Leeches were applied to the larynx and the trachea for bronchitis and laryngitis and for relieving the cough of phthisis. For inflammations of the conjunctiva (the membrane lining the eyelids) they were applied to the nasal membrances of the adjacent nostril, and for inflammations of the ear they were applied to the meatus of the ear and behind the ear. The French popularized the practice of leeching the anus to treat inflammations of the mucous membranes of the bowel. To prevent leeches from getting lost in the body cavities, Jonathan Osborne, a British physician, recommended in 1833 that a thread should be passed through the leech's tail. In addition, he invented a device, which he called a "polytome," specifically for introducing leeches into the rectum.[179] In the mid-nineteenth century, special leech tubes were widely sold for applying leeches to internal membranes.[180] A second advantage of leeches over cupping was that leeches could extract blood more readily. Not only was dexterity not required in order to apply a leech, but also it was soon noticed that leech bites continued to bleed even after the leech let go, while scarificator incisions often coagulated before any blood was obtained. In 1884 it was shown by John Berry Haycroft, a Birmingham chemist, that this phenomenon was due to an anti-coagulant, now called "hirudin," that the leech injected into the blood.[181] To apply a leech, the animal was first dried with a bit of linen, and the skin of the patient was prepared by washing with warm water and then shaving. To direct it to the right spot, the leech was often placed in a small wine glass that was inverted over the area to be bitten. Since leeches were sometimes perversely unwilling to bite, they were enticed by the placement of a bit of milk or blood on the patient's skin. Small children were given one or two leeches, and adults 20 or more. Broussais employed up to 50 leeches at one time.[182] The leech was usually allowed to drop off of its own accord when it had satiated itself, which took about an hour. Sometimes the tail of the leech was cut off so that it would continue to suck. Once used, leeches could not be reused for several months unless they were made to disgorge their meal by dropping them in salt water or weak vinegar. A healthy leech drew one or two fluid drachms of blood, and as much would flow after the leech had dropped off. Thus a good Swedish leech could remove about an ounce of blood. This quantity could be increased by employing a cupping glass over the bite.[183]