296 OF THE PRIMARY TISSUES OP THE HUMAN BODY. 



upon the anterior parietes of those cavities, and cause their absorption; so that 

 each tooth is allowed to come forwards, in some degree, into the lower part of the 



socket of the corresponding " temporary" tooth. 

 Fig. 86. The root of the temporary tooth now begins 



to be absorbed, generally at the part nearest 

 its successor (Fig. 86); and this absorption 

 proceeds as the new tooth advances, until the 

 root of the "milk" tooth is completely re- 

 moved; when its crown falls off, leaving room 

 for the permanent tooth to supply its place 

 (Fig. 84, p t). This absorption is usually 

 regarded as due to the pressure of the perma- 

 nent tooth, but such does not appear to be the 

 case ; for it is mentioned by Mr. Bell, that it 

 is not an uncommon occurrence for the root of 

 the temporary tooth to be wholly absorbed, and 

 for the crown to fall out spontaneously, long 



Section of portion of the upper jaw of a ^ fore the Succeeding tooth has approached 

 child, showing a new tooth in process of Vacant Space. The Same has been re- 

 formation, the fang of the corresponding marked by Mr. Bell, of the cavity in the jaw 

 deciduous tooth being absorbed. which is formed for the reception of the sac 



of the " permanent" tooth, at the time that it 



buds off from that of the "milk" tooth; the excavation being often seen to com- 

 mence before the new sac is formed. Hence, although the two processes, growth 

 and absorption, are usually contemporaneous in each instance, they are by no 

 means dependent on each other. Still, it would seem that the existence, if not 

 the pressure, of the new tooth is necessary to determine the absorption of the 

 old; for cases are not unfrequent, in which the temporary teeth retain their 

 situation in the mouth, with considerable firmness, until adult age the corre- 

 sponding permanent ones not having been formed. 



290. In the successive replacement of the " milk" teeth by the " permanent" 

 set, a very regular order is usually followed. The middle incisors are first shed 

 and renewed, and then the lateral Incisors. The anterior " milk" Molars next 

 follow; and these are replaced by the anterior Bicuspid teeth. About a year 

 afterwards, the posterior " milk" Molars are shed, and are replaced in like manner 

 by Bicuspid teeth. The Canines are the last of the "milk" teeth to be ex- 

 changed ; the development of the new ones not taking place until the 12th year. 

 In the succeeding year, the second pair of the true Molars appears ; the third 

 pair, or denies sapientiae, are seldom developed until three or four years subse- 

 quently, and often much later. It has been proposed 1 (and, from the evidence 

 adduced in its favor, the proposition would seem entitled to considerable atten- 

 tion) to adopt the successive stages in the Second Dentition, as standards for 

 estimating the physical capabilities of Children, especially in regard to those 

 two periods which the Factory Laws render it of the greatest importance to 

 determine, namely, the ages of nine and thirteen years. Previously to the former, 

 a Child is not permitted to work at all; and up to the latter, it may be only 

 employed during nine hours a day. The necessities or the cupidity of Parents 

 are continually inducing them to misrepresent the ages of their children ; and 

 it has been found desirable, therefore, to seek for some test, by which the capa- 

 bility of the Child may be determined, without a knowledge of its age. A 

 standard of Height has been adopted by the Legislature for this purpose ; but 

 upon grounds which, physiologically considered, are very erroneous ; since, as 



1 " The Teeth a Test of Age, considered with reference to the Factory Children." By 

 Edwin Saunders. 



