ANIMAL DENTITION. 
BY 
R. LyDEKKER. 
I. MAMMALS. 
Fig. 1. Dentition of Double-Tusked Fox. 
I WAS once asked by a seeker after zoological knowledge to enlighten him on the 
subject of “Animal Dentistry.” Naturally 1 was somewhat astonished, as I cannot 
claim any knowledge of the proper way to extract a lon’s tusks or to stop an 
elephant’s molar; and I may add that I have no particular desire to learn such 
accomplishments. Further conversation soon showed me that the term “dentistry” 
was only my interviewer's ultra-popular synonym for the word “ dentition,’ and on 
my return home I consulted a dictionary to find out if there was justification for the 
former usage. The result of my search was to find, as I expected, that “dentistry ”’ 
indicates only the surgical treatment of teeth. I was, however, somewhat surprised 
to learn from the same source that “dentition” properly means “the breeding or 
cutting of teeth in infancy; the time of breeding teeth.” Strictly speaking, therefore, 
this term has no more right to be used in the sense in which it is employed by 
naturalists—that is to say, to designate the general characters and number of the teeth 
of animals—than the word “dentistry.” Since, however, its employment in this sense 
is now universal in the scientific world, I make no apology for continuing to follow 
this usage. If my readers desire a more thoroughly technical term, “odontology” (that 
is to say, the science of teeth) is at their service. 
So much by way of preliminary. JI now pass on to my proper subject, in which, 
from its extent, I find a great difficulty in knowing where and how to commence. 
Perhaps the most essential features in connection with the dentition of mammals 
are, firstly, that the teeth are confined to the margins of the jaws, where they form 
a single row, and, secondly, that (with the exception of certain aberrant types such as 
whales, dolphins, and manatis) their number is strictly limited and definite. Not less 
important is the fact that only two sets of teeth are ever developed during the whole of 
life, namely, a milk, or baby, set, which is shed in youth, and a permanent series, 
which has to do duty for the remainder of the term of its owner’s existence (Fig. 2). 
Sometimes there is not even this single replacement, and only one set is developed. 
In all cases the teeth are implanted in separate sockets, and very generally those of the 
hinder part of the series have 
two or more roots. 
Another essential feature of 
the dentition of most mammals 
is that the teeth in different 
parts of the jaw are unlike 
one another. Commonly, as for 
Instance in a dog or a fox, the 
dentition is divisible into three 
well-marked series. First of all 
we have the single pairs of tusks, 
Fig, 2. The Permanent (upper line) and ‘‘Baby”’ (lower line) Teeth of the 3 3 
right side of the upper jaw of a Dog, removed from their sockets. or canines, In each jaw, of which 
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