Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

or else through the intercellular substance, form a plexus under the enamel which is highly sensitive. Every prac- titioner knows, that in excavating some teeth there is no pain whatever felt on introducing the instrument even into the pulp cavity itself; but that a sharp pang is experienced imme- diately if we touch the spot where the dentine and enamel come in contact. The sensibility, however, of this membrane need not interfere with plugging the tooth ; no ill effects will follow it. That which is toothache, in the general acceptation of the word, proceeds rather from the actual exposure of the dental pulp, and is characterized by acute and violent pain. A por- tion of food, or any foreign substance, entering the cavity of the tooth and coming in contact with the pulp, — anything very hot or cold, — in fact, if only exceeding in either of these respects the natural temperature of the mouth, immediately produces a paroxysm of pain along the whole course of the dental nerve, extending up the head, &c. There are three modes of treatment open to the dentist in these cases. Should the affected tooth be one of the incisors or canines, the pulp may be removed either by a five-sided broach, or by pushing a straightened small fish-hook up the cavity of the tooth, giving it then a half turn, and withdrawing it quickly, and in nine cases out of ten you will bring along the nerve with it. The bleeding then may be stopped by the application of camphorated spirit; after which, remove all the carious bone, dry out the cavity, and plug it. The second plan is to destroy the nerve entirely. The third plan is to render the exposed surface insensible. After speaking of the employment of arsenic, creosote, tannic acid, quicklime, and nitrate of silver, he proceeds to say, " The actual cautery (by galvanic heat) may often be resorted to with great success in instantly producing an eschar on the sensitive pulp, and in a few days the tooth may be filled. You first apply the wire of the cauterizer to the affected pulp unheated; then, by touching a spring, contact is made with the battery, and the wire is instantly at a white heat. Care should be taken not to wound the internal (deep) part of the pulp."