2 5 8 



NATURAL SCIENCE. 



April, 1895. 



not grow to any great length (Fig. D.), and the roots are formed very 

 early, beginning even three months before birth. Calcification of the 

 deciduous molars commences at about five and a half months before 

 birth, and their eruption occurs a few days after birth. The first two 

 deciduous molars (dm 2 and 3) are shed at two years and a half, the 

 third (dm 4) a year later. The premolars cut the gum a few weeks 

 after the shedding of their respective milk predecessors, and are 

 retained for life. The first true molar cuts the gum at about ten 

 months after birth, the second between twenty months and two years, 

 and the third, which only begins to calcify at two years, is cut at 

 three years and three-quarters. 



The following table, based largely on the classical observations 

 of Girard, Mayhew, and Lecellier, as corrected by the more modern 

 authorities, Brown, Goubaux and Barrier, Chauveau, and others, is 

 here appended, with a view to showing at a glance the average 

 dates at which the calcification, eruption, and shedding of the various 

 teeth take place. 



Teeth. Calcification. 



di 1 6 months before birth 



di 2 5 months before birth 



di 3 1 month before birth 



i 1 ? 1 year 



12 1^ years 



i 3 3 years 



dc 2 weeks before birth 



c ? 2 years 



pm 1 4 months before birth 



dm 2 5J months before birth 



dm 3 5^ months before birth 



dm 4 5i months before birth 



pm 2 1 year 



pm 3 1 year 



pm 4 20 months. 



m 1 2 weeks before birth 



111 2 4 months 



m 3 2 years 



Eruption. 



A few days alter birth 

 6 weeks 

 8 months 

 i\ years 

 3^ years 

 4i years 



Absorbed without eruption 

 5 years I 



(Eruption rarely oc- > 

 curs in the female.) ) 

 ? 3 months j 



(Frequently absorbed > 

 ■ without eruption.) J 



A few days after birth 

 A few days after birth 

 A few days after birth 

 z\ years 

 i\ years 

 3J years 

 10 months 

 22 months 

 3! years 



Shedding. 



i\ years. 

 3 \ years. 

 4 1 years. 



3 to 4 years. 



2^ years or later. 



2J years. 

 i\ years. 

 l\ years. 



W. G. RlDEWOOD. 



