Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/180

 176 detail, as they afford coincidences with the bones in the corresponding parts of Lizards, from which important conclusions may be derived.

As an insulated fact, it may seem to be of little moment, whether a living Lizard or a fossil Pterodactyle, might have four or five joints in its fourth finger, or its fourth toe; but those who have patience to examine the minutæ of this structure, will find in it an exemplification of the general principle, that things apparently minute and trifling in themselves, may acquire importance, when viewed in connexion with others, which, taken singly, appear equally insignificant. Minutiæ of this kind, viewed in their conjoint relations to the parts and proportions of other animals, may illustrate points of high importance in physiology, and thereby become connected with the still higher considerations of natural theology. If we examine the fore-foot of the existing Lizards, (Pl. 22, B.) we find the number of joints regularly increased by the addition of one, as we proceed from the first finger, or thumb, which has two joints, to the third, in which there are four; this is precisely the numerical arrangement which takes place in the three first fingers of the hand of the Pterodactyle; (Pl. 22, C. D. E. N. O. Figs. 30—38.) Thus far the three first fingers of the fossil reptile agree in structure with those of the forefoot of living Lizards; but as the hand of the Pterodactyle was to be converted into an organ of flight, the joints of the fourth, or fifth finger were lengthened, to become expansors of a membranous wing.