The socket of the permanent tusk in a new born Elephant is a round cell about three lines in diameter, situated on the inner and posterior side of the aperture of the temporary socket. The permanent tusks cut the gum when about an inch in length, a month or two usually after the milk teeth are shed. The widely-open base of the tusk is fixed upon a conical pulp, which, with the capsule surrounding the base, progressively increases in size, stimulates a concomitant increase in the capacity and depth of the socket, which cavity soon obliterates that of the deciduous tusk.
These incisive teeth of the Elephant not only surpass other teeth in size, as belonging to a quadruped so enormous, but they are the largest of all teeth in proportion to the size of the body, representing in a natural state those monstrous incisors of Rodents which are the result of accidental suppression of the wearing force of the opposite teeth.
The molar teeth of the Elephant are remark able for their great size, even in relation to the bulk of the animal, and for the extreme corn= plexity of their structure. The crown, of which a great proportion is buried in the socket, and very little more than the grinding surface ap pears above the gum, is deeply divided into a number of transverse perpendicular plates, consisting each of a body of dentine, coated by a layer of enamel, and this by a less dense bone-like substance which fills the interspaces of the enamelled plates, and here more espe cially merits the name of cement, since it binds together the several divisions of the tooth before they are fully formed and united by the confluence of their bases into a common body of dentine.
The rnanner in which these complex teeth are formed is a subject of great interest, and has been ably investigated by many celebrated anatomists, particularly by the two Campers, father and son, M. Corse, Itobert Blake, and John Bunter, whose splendid preparations illus trative of the process are contained in the Museum of the Royal College of Surgeons in London. It is to Cuvier, however, we are indebted for the most complete and lumi nous exposition of this important piece of physiology, as may he gathered from the fol lowing account extracted from his great work, " Recherches sur les Ossemens Fossiles." " The molar tooth of the Elephant, like every other marnmiferous tooth, is formed in the in terior of a membranous sac, now generally called the capsule of the tooth. This capsule
has in the Elephant a rhomboidal form, and is closed on all sides, excepting the small open ings for the passage of nerves and vessels. It is lodged in a bony cavity of the same shape as itself, excavated in the maxillary bone, which afterwards forms the socket of the tooth." " It is, however, only the external lamina of the capsule which is thus simple in its arrange ment, the inner lamina being, as in all other herbivorous animals, thrown into numerous folds, as will be understood when we have described the pulp upon which the tooth is formed." " This pulp has in every animal its pectilir. arrangement. To represent that of the Ele phant, we must imagine that from the bottom of the capsule as from a base, there arise nu merous parallel and transverse walls which mount upwards towards that part of the cap sule which is placed next to the gums. These little walls are only adherent to the floor of the capsule, their opposite extremity or summit being free from all adherence." " The free summit is much thinner than the base, so that it might be called the edge, and is moreover deeply cleft in many parts, so as to form numerous sharp points and indentations. The substance of these little walls is soft, trans parent, and very vascular, containing appa rently much gelatine : it becomes hard, white, and opaque in spirits of wine." " It will be now easy to understand the manner in which the inner membrane of the capsule is folded, if we imagine it to form pro longations which penetrate into all the intervals between the little walls above described. These prolongations adhere to the upper part of the capsule, that is, to the side of it which is nearest the gums, and also to its lateml parietes, but. are not adherent to its base, from whence the little gelatinous walls above described arise. Consequently it is easy to understand that there may be a continuous cavity amazingly folded upon itself, extending between all the gelati. nous walls (which are descPnding in the upper teeth, ascending in the lower teeth) and these membranous partitions (ascending in the upper teeth, descending in the lower teeth.)" " It is in this conceivable cavity that the ma.