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206 by Mr. Smith in the “Philosophical Transactions” for 1818. This tube, although completely enclosed, excepting at its basal and apical orifices, must be considered as formed merely by the closing round of a groove in the external part of the tooth itself, and hence not in any way connected with the inner cavity of the tooth, in which exists the pulp upon which the substance of the tooth is formed. The base of the tooth, and consequently the basal orifice of the tube just described, is embedded in a sac, into which the poison is poured from the ducts of the glandular structure by which it is secreted, and which is believed to represent the parotid gland of the higher Vertebrata. The poisonous fluid itself is inodorous, tasteless, and of a yellow colour. It is secreted in greater quantity, and its qualities are more virulent in a high temperature than in cold. Its secretion may be greatly increased by local irritation; as is evidenced by the following fact. Some years since I was dissecting very carefully and minutely the poison apparatus of a large Rattlesnake, which had been dead for some hours; the head had been taken off immediately after death, yet as I continued my dissection the yellow poison continued to be secreted so fast as to require to be occasionally dried off with a bit of rag or sponge; I believe that there could not have been less altogether than six or eight drops at the least.

“When the animal inflicts the wound, the pressure on the tooth forces a small drop of the poison through the tube; it passes through the external orifice, which is situated on the concave side of the curved tooth, and is in the form of a