1854.] OF THE ROYAL INSTITUTION, 369 
teeth have been called dentes serrati. But the philosophical course 
of the knowledge of nature tends to explode needless terms of art, 
invented for unimportant varieties, and to establish and fix the 
meaning of those words that are the signs of determinate species 
of things. 
The Cuviers divided the molar series of teeth, according to their 
form, into three kinds: ‘‘ false molars,” ‘‘ carnassials,”’ and ‘‘ tu- 
bercular molars ;’’ and, in giving the generic characters of 
Mammalia, based the dental formule on this system: thus the 
genus Felis is characterised as having “ fausses molaires —- 
a sastlase avimals ee SSS 
carnassi¢res >> tuberculeuses 5 5 => 
In a diagram of the leading modifications of Diphyodont denti- 
tion, an uninterrupted line marked ‘‘ Cuvier” was made to intersect 
the teeth in each jaw of the Carnivora, called by that great anato- 
mist, ‘‘carnassiéres ;” those anterior to them being the teeth which 
he called “‘ fausses molaires ;” those behind being the “ tubercu- 
leuses.” Most zoologists, both at home and abroad, have adopted 
the Cuvierian system of formulising the molar teeth. Prof. De 
Blainville, however, abandoned that classification of the molar 
series, without assigning his objections to it ; and proposed another, 
in which he divides the series into “‘avant-molaires,” “principales,” 
and “ arriére-molaires ;” he exemplifies this division by the human 
dentition, in which the five grinders on each side of both jaws are 
formulised as ‘‘two avant-molaires, one principale, and two 
arriere-molaires.” The teeth regarded by De Blainville as the 
homologues of these, were indicated in the diagram above referred to 
by a dotted line intersecting the “dent principale” in each species. 
Truly homologous teeth are determined, like other parts, by 
their relative position, by their connections, and by their de- 
velopment. The teeth of one side of the jaw repeat, are an- 
swerable to, or are homotypes, of the teeth on the other side ; and 
those in the upper jaw usually correspond, in like manner, to 
those in the under jaw. 
Those teeth which are implanted in the premaxillary bones, 
and in the corresponding part of the lower jaw, are called © 
“incisors, whatever be their shape or size. The tooth in the 
maxillary bone, which is situated at, or near to, the suture with 
the premaxillary, is the “canine,” as is also that tooth in the 
lower jaw which, in opposing it, passes in front of its crown 
when the mouth is closed. The first-formed incisors and canines 
are deciduous; they are succeeded and displaced vertically by 
the permanent incisors and canines. With regard to the other 
teeth, their true nature, and homologies, about which the dif- 
ference of opinion has chiefly prevailed amongst anatomists, are 
determinable not by shape or size, or by relative position to the 
