ON THE TEETH. 
369 
respects its correctness, I must still be allowed to make a few re- 
marks on that gentleman’s statements, in which my observations 
have shewn different results. 
The temporary molar teeth I have always found are shed about 
the completion of the third year, within a short time of each 
other ; and repeated observation has led me to the conclusion, that 
the average period of the year at which they are shed is between the 
months of April and June. This, of course, is not always regular, 
as being an earlier or later foal, or having some peculiar idiosyn- 
cracy, may make it irregular, not only as to the period at which the 
change is completed, but also between the teeth in their relative 
position of completion. The first changes generally are in the teeth 
of the upper jaw : these are followed by the opposing teeth in 
the lower jaw. The first temporary upper molar is thrown off : 
this is soon followed by the lower first molar ; this by the second 
upper, then the second lower, third upper, and completed by the 
third lower molar. The time that elapses between these changes 
is nearly equally divided, the period between the throwing off of 
the first and second molar being rather the longest. If the teeth of 
a two year and nine months colt be examined, it will be apparent 
that such is the case, as the difference in thickness of the shells is 
but slight, and may stand in relative proportion thus : 4-16ths, 
6-16ths, 7-16ths of an inch in thickness. It has never occurred 
in the course of my observations upon the changes during dentition 
to meet with an instance of the third molar not being completed 
until nearly four years old ; on the contrary, I have generally found 
the process complete by three years and six months ; that is, by 
the time the second incisors are to be thrown off. I have given 
the average periods, as shewn by the result of my own observa- 
tions. Of course, during a long course of practice, I have met 
with many varieties and exceptions; but in a subject like the one 
now agitating the sporting world, the object is not to bring forward 
partial views or exceptions to general rules, but clearly to point 
out the form of and time when changes most generally take place. 
The teeth of herbivorous animals are always growing, the molars 
more than the incisors. In this particular they differ from those of 
the carnivora. This will be still more apparent if we consider the 
different uses to which these opposite classes apply their teeth. 
The food of the herbivora is large in bulk, and requires to be 
ground down into a perfect pulp ; on the contrary, the carnivora 
require only to chop their food into such portions as can be swal- 
lowed : they are furnished with sharp angular teeth, covered with 
an external coating of enamel, which from its hardness keeps sharp 
the angles, and wears but very slowly. Their teeth thus enclosed 
in enamel never grow after their permanent completion. The teeth 
VOL. XVIII. 3 E 
