Academy of Sciences in Paris. 381 



that is the name of those teeth which, in the human mouth, present 

 themselves the first in going from front to back. If the inverse 

 course had been adopted, and the calculation made from the hinder 

 part of the jaw, those teeth which, in the rongeurs, come after the 

 molares, would, for the same reason, have been called canine. M. 

 St. Hilaire's object is to ascertain which of the two appellations is 

 intrinsically correct. It is evident that one class of teeth is entirely 

 wanting, and this deficiency may be considered as the result of an 

 atrophy. This atrophy must have existed either at the middle of the 

 jaws, or one of the extremities ; and M. Geoffrey conceives that the 

 latter hypothesis is alone admissible, and that the atrophy must have 

 occurred at the point at which the maxillary branch terminates. 

 When the length of jaw gives sufficient room for the full develop- 

 ment of the dental nerve, as in the dolphin, the lizard, the crocodile, 

 &c., the dental, arterial, venous, and -nervous branches are subdivided 

 into clusters, of similar volume, and equally distributed. Then 

 there are as many conic and symmetrically arranged teeth as there 

 are subdivisions in the parent branches. There is then a regular 

 formation in every point, both anteriorly and posteriorly; and it is of 

 little or no consequence to what zoological class the animal belongs, 

 since it is not the organic difference, but the room which exists for 

 the development and distribution of the vascular and nervous branches, 

 which makes the distinction. Hence we may conclude that there is 

 nothing specially inherent in the nature of the dental operations to 

 occasion the division of the teeth into the three classes of incisors, 

 canine, and molares. The want of one class of teeth in the rongeurs 

 is, therefore, owing to the want of room for development; the 

 development began with the molares, which are, unquestionably, 

 there; then proceeded with the canine teeth; but being there stopped 

 for want of room, ceased, and the incisors are consequently wanting. 

 There is no reason why we should admit the existence of the two ex- 

 tremes of the molares and the incisors, and suppose the absence of 

 the intermediate class, the canine. The front teetli of the mammi- 

 ferae rongeurs should, therefore, as a matter of consistency, be called 

 canine, and not incisors. 



On the 18th, M. St. Hilaire read another memoir relating to the 

 same subject ; the object of which was to correct an error into which, 

 the learned academician stated, that he considered himself to have 

 fallen, in common with M. Cuvier, in 1795 ; when they published a 

 memoir, in which the existence of the. inter-maxillary bone was con- 

 sidered as furnishing a certain criterion for attributing to teeth affixed 

 in it the character of incisors. This opinion M. St. Hilaire now 

 considers erroneous: 1. Because it can only apply to the upper jaw, 

 and, therefore, leaves the teeth of the lower jaw subject to an arbi- 

 trary classification ; and, 2. because, so far from the inter-maxillary 

 bone being merely intended to support the incisors, that bone exists 

 in a great number of animals which have no teeth at all in the an- 



