. On the anatomy of vertebrates [electronic resource] . astmolar. It does not appearthat the scalpriform incisors,ib. i, are preceded by milkteeth, or, like the premolarsdiz a\ m of the Guinea-pig, by ute- ^li^f|P?ll^ rine teeth; but the second incisor, ib. i, 2, is so preceded Upper deciduous and permanent teeth of the Hare. 1 — by the tooth markedd, i, 2, at which period of dentition six incisors are present in theupper jaw. This condition is interesting both as a transitory mani-festation of the normal number of incisive teeth in the mammalianseries, and as it elucidates the disputed na
. On the anatomy of vertebrates [electronic resource] . astmolar. It does not appearthat the scalpriform incisors,ib. i, are preceded by milkteeth, or, like the premolarsdiz a\ m of the Guinea-pig, by ute- ^li^f|P?ll^ rine teeth; but the second incisor, ib. i, 2, is so preceded Upper deciduous and permanent teeth of the Hare. 1 — by the tooth markedd, i, 2, at which period of dentition six incisors are present in theupper jaw. This condition is interesting both as a transitory mani-festation of the normal number of incisive teeth in the mammalianseries, and as it elucidates the disputed nature cf the great anteriorscalpriform teeth of the Rodentia. It has been contended thatthey are canines, because those of the upper jaw extendedtheir fang backward into the maxillary bone, which lodged partof their hollow base and matrix. But the scalpriform teeth areconfined exclusively to the premaxillary bones at the beginningof their formation, and the smaller incisors which are developedbehind them, in our anomalous native Rodents, the Hare and. TEETH OF DIOPHYODONTS. 301 Rabbit, retain their usual relations with the premaxillaries, thusproving, a fortiori, that the tooth which projects anterior to themmust also be an incisor. The law of the unlimited growth of the scalpriform incisors isunconditional; and constant exercise and abrasion are requiredto maintain the normal and serviceable form and proportions ofthese teeth. When, by accident, an opposing incisor is lost, orwhen, by the distorted union of a broken jaw, the lower incisorsno longer meet the upper ones, as sometimes happens to a woundedhare, the incisors continue to grow until they project like thetusks of the elephant, and their extremities, in the poor animalspainful attempts to acquire food, also become pointed like the curve prescribed to their growth by the form oftheir socket, their points often return against some part of thehead, are pressed through the skin, 239then cause absorption of
Size: 3045px × 821px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubject, booksubjectbirds, booksubjectfishes
