[93] Ib.
Such is Cuvier’s outline of the earlier history of comparative anatomy. We shall not go into detail upon this subject; but we may observe that such studies had fixed in the minds of naturalists the conviction of the possibility and the propriety of considering large divisions of the animal kingdom as modifications of one common type. Belon, as early as 1555, had placed the skeleton of a man and a bird side by side, and shown the correspondence of parts. So far as the case of vertebrated animals extends, this correspondence is generally allowed; although it required some ingenuity to detect its details in some cases; for instance, to see the analogy of parts between the head of a man and a fish.
In tracing these less obvious correspondencies, some curious steps have been made in recent times. And here we must, I conceive, again ascribe no small merit to the same remarkable man who, as we have already had to point out, gave so great an impulse to vegetable morphology. Göthe, whose talent and disposition for speculating on all parts of nature were truly admirable, was excited to the study of anatomy by his propinquity to the Duke of Weimar’s cabinet of natural history. In 1786, he published a little essay, the object of which was to show that in man, as well as in beasts, the upper jaw contains an intermaxillary bone, although the sutures are obliterated. After 1790,[94] animated and impelled by the same passion for natural [477] observation and for general views, which had produced his Metamorphosis of Plants, he pursued his speculations on these subjects eagerly and successfully. And in 1795, he published a Sketch of a Universal Introduction into Comparative Anatomy, beginning with Osteology; in which he attempts to establish an “osteological type,” to which skeletons of all animals may be referred. I do not pretend that Göthe’s anatomical works have had any influence on the progress of the science comparable with that which has been exercised by the labors of professional anatomists; but the ingenuity and value of the views which they contained was acknowledged by the best authorities; and the clearer introduction and application of the principle of developed and metamorphosed symmetry may be dated from about this time. Göthe declares that, at an early period of these speculations, he was convinced[95] that the bony head of beasts is to be derived from six vertebræ. In 1807, Oken published a “Program” On the Signification of the Bones of the Skull, in which he maintained that these bones are equivalent to four vertebræ); and Meckel, in his Comparative Anatomy, in 1811, also resolved the skull into vertebræ. But Spix, in his elaborate work Cephalogenesis, in 1815, reduced the vertebræ of the head to three. “Oken,” he says,[96] “published opinions merely theoretical, and consequently contrary to those maintained in this work, which are drawn from observation.” This resolution of the head into vertebræ is assented to by many of the best physiologists, as explaining the distribution of the nerves, and other phenomena. Spix further extended the application of the vertebral theory to the heads of all classes of vertebrate animals; and Bojanus published a Memoir expressly on the vertebral structure of the skulls of fishes in Oken’s Isis for 1818. Geoffroy Saint-Hilaire presented a lithographic plate to the French Academy in February 1824, entitled Composition de la Tête osseuse chez l’Homme et les Animaux, and developed his views of the vertebral composition of the skull in two Memoirs published in the Annales des Sciences Naturelles for 1824. We cannot fail to recognize here the attempt to apply to the skeleton of animals the principle which leads botanists to consider all the parts of a flower as transformations of the same organs. How far the application of the principle, as here proposed, is just, I must leave philosophical physiologists to decide.
[94] Zur Morphologie, i. 234.
[95] Zur Morphologie, 250.
[96] Spix, Cephalogenesis.
By these and similar researches, it is held by the best physiologists [478] that the skull of all vertebrate animals is pretty well reduced to a uniform structure, and the laws of its variations nearly determined.[97]
[97] Cuv. Hist. Sc. Nat. iii. 442.
The vertebrate animals being thus reduced to a single type, the question arises how far this can be done with regard to other animals, and how many such types there are. And here we come to one of the important services which Cuvier rendered to natural history.