Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . Fig. 22.—Development or Teeth.—a, thegum; b, the lower jaw; c, dental capsules. Fig. 23.—Dental Capsule. 145. The first set, or milk teeth, {fig. 22,) are twenty inn amber—four incisors in the front of each jaw, and twocanine and four molar teeth on each side. All these teethfall out at from six to eight years of age, and are gradu-ally replaced by the permanent teeth, {fig. 23,) which are. Fig. 23.—Hum
Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . Fig. 22.—Development or Teeth.—a, thegum; b, the lower jaw; c, dental capsules. Fig. 23.—Dental Capsule. 145. The first set, or milk teeth, {fig. 22,) are twenty inn amber—four incisors in the front of each jaw, and twocanine and four molar teeth on each side. All these teethfall out at from six to eight years of age, and are gradu-ally replaced by the permanent teeth, {fig. 23,) which are. Fig. 23.—Human Teeth.—o, incisors; b, canine tooth ; c, bicuspid teeth; d, molars. thirty-two in number, sixteen in each jaw, namely: fourincisors, two canine, four bicuspids or small molars, andsix true molars. The last molar does not make its appear-ance until long after the rest, and hence it is called thewisdom-tooth. 146. The human teeth are composed of three distinct Describe each. How many sets of teeth are there ? How many teeth arethere in the first set ? How many in the second ? When does the last mo-Jar make its appearance ? Of what are the human teeth composed? 70 CLASS-BOOK OF PHYSIOLOGY. structures—the ivory or tooth-bone, the enamel, and thecementum. The ivory, which constitutes the main part ofof the tooth, resembles bone in its structure, except it con-tains a larger amount of mineral matter, and is harderthan bone. The enamel forms a crust over the whole sur-face of the crown of the tooth, and protects it from wear-ing out or decaying. It is composed of ninety-
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