15 G HISTOKY OF THE WOEKS OF CUVIER. 



"hone^ but composed of four bones, as it is in the foetal mammals, tbe squamosal, 

 the mastoid, the cavity of the tympanum, and the petrous bone. There remained 

 only the bones Avhicli correspond to the frontal to reduce to analogy, but these 

 bones are six in number in the crocodile, and as the frontal of mammifers is never 

 divided but into two, M. Ouvier was obliged to admit here a peculiar dismem- 

 berment of this bone, a dismemberment wliich, in the crocodile, or, to speak more 

 generally, in the greater part of oviparous vertebrates, subdivides each of the 

 two frontals of mammals into thi'ee others, the principal, the anterior, and the 

 posterior frontals. 



This determination of the bones of the head of the crocodile, compared with 

 those of the head of mammals, being once established, it is easy to refer to it, as 

 a sort of type, the bones of the head of all other reptiles, jiarticularly tortoises, 

 lizards, and serpents. Thus, with due regard to the differences of form and pro- 

 portion, the greater part of the bones of the crocodile reappear in the head of the 

 tortoise ; but this head wants the nasal bones, which are here represented only 

 by cartilaginous laminge, the transverse or external pterygoid and the lachrymal 

 bones. Moreover, the parietal, which is single in the crocodile, is double in the 

 tortoise ; but in the lizards this parietal again becomes single, the lachrymal and 

 transverse bones reappear, a new bone is disclosed which M. Cuvier calls columella, 

 &c.; all but slight differences, v/hich do not hinder us from recognizing throughout 

 the predominance of one same plan in the heads of the crocodile, the tortoise, 

 and the lizard. 



A new and more difficult study commences with the hafrachians. First, the 

 general composition of the head is singularly simplified. We find here only the 

 two lateral occipitals, with neither upper occipital nor basilar; a single sphenoid 

 with neither temporal nor orbital wings ; a single bone replaces at once the 

 principal frontal and the ethmoid ; there are no posterior frontals, but there are 

 two anterior frontals, two parietals, and two petrous bones. Nor is the face less 

 simplified, for the transverse forms only one with the pterygoid, the temporal but 

 one with the t3nnpanic, and there is no mastoid. The cranium of the frog, there- 

 fore, has but 10 bones, one ethmoid, two frontals, two parietals, two occipitals, 

 one sphenoid, two petrous bones: its face has but 16, two intermaxillars, two 

 niaxillars, two nasals, two palatines, two vomers, two pterygoids, two tympanies, 

 and two jugals or zygomatics. In all, its head has but 26 bones, while that of the 

 crocodile has nearly 40. And this difference of number presents itself in each par- 

 ticular apparatus of the face ; thus the lower jaw of the crocodile has six bones 

 on each side, and each side of the jaw of the frog has but three, &c. 



I have said that the apparatus of the vertehrce is, with that of the cranium, the 

 most constant ; each vertebra may itself be considered as a small distinct appa- 

 ratus, composed of a certain number of bones, which is not the same for all the 

 vertebrae in each species, nor for each vertebra in all the species; the atlas of 

 the crocodile has six bones, its axis has five ; the atlas of the tortoise has only 

 four, that of the monitor three, &c. But it is chiefly by their total nuurber that 

 the vertebrae vary from one class to the other, and even in the different orders, 

 the different genera of each class. Not to depart here from the reptiles, the 

 crocodile, for example, has 26 vertebrae — 7 cervical, 12 dorsal, 5 lumbar, and 2 

 sacral ; 200 are counted in the adder, the boa, &c. ; the frog has but nine. As 

 regards other apparatus of the animal system, being only accessory, the greater 

 part may be wanting, and is wanting, in effect, in such or such a class, such or 

 such an order, such or such a genus, &c. The hinder extremities fail in the 

 cetacea, both the anterior and posterior extremities in the serpent, the ribs are 

 absent in the frog, the auricular apparatus in fishes, &c. 



Nothing is better calculated to give a just idea of the manner in which a certain 

 general conformity is combined in certain cases with all the variations of detail 

 than what is seen in the shoulder and the sternum. The shoulder, which is com- 

 posed, in the mammifer, of but one bone, the scapula, or of two, the scapula and 



