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Show 286 ON THE STRUCTURE OF THE VERTEBRATE SKULL. cesses; the two frontals form the spinous process, together with its lateral parts. . "The sphenoid is separated into two vertebr~, not merely ~n t l1 e I1 uman .1r0 0t us and I·n Ruminants, bnt also In the A pes, 111 B dy_,'YJUS tridactylus Dasypus novemcinct~c.s, Dog, Wolf, Bear, Orttae r, rR odents, and p' robably in all Mamma1 s , I' f . d . ~xainine In a sufficiently young state. The law is therefore universal. "The inter-vertebral foramina are very wellinarked between these vertebrre. A deviation seems to exist, on account of the foramina which lie in front of the first cephalic vertf' bra, namely, the foramen caroticum and laceru·m, c~n~erning which I must leave it undecided, whether they are ong1nally two, or only one which has become separated. On this point evidence enough is to be found among animals. The organ of hearing has here interposed itself. On the other hand, it is characteristic of the cephalic vertebrre that their sides are perforated by ner~es,by the optic nerve, the jaw nerves, and ~he hypoglossus, If we reckon the auditory and facial nerves as Inter-vertebral nerves: a circumstance which demands further inquiry. "So much of the cephalic vertebral column. I might have been able to treat more fully and thoroughly of it, and to have indicated the nerves, veins, and mu cl s, which in the head correspond to those of the trunk, and the !ike for the bo~1es; but in a programme one must be content With merely puttmg forth one's view of a question. "II. "If the cerebral capsule is the r petition of the spinal column, only more expanded and organized (I speak as. an anatomist), the head Inust repeat the outgrowths of the. spinal column, the thorax, the pel vis, and the limbs; and, Indeed, thereby must it attain con1pleteness. "By this union of the representatives of all the b?nes of the trunk arises the wonderful, but yet analysable, mixture and intercurrence of formations which app ar as the facial bones. rrhe spinal column becomes the brain-cas ; the walls of the trunk with the extremities, become the face." I~ developing this idea, Oken arrives at the conclusion t]~at the nasal cavity is the thorax of tho head, and the oral cavity THE 'l'HEORY OF THE VER'l'EBRATE SKULL. 287 the abdorne~ .of the head. Tho squamosal is the conjoined sca~ula and Ihum of the hearl; the pterygoid, the clavicle; the hyoidean apparatus, the other pel vic bones. The jugal arch represents the humerus, radius, and ulna; the- maxil1a, the hand ; .the premaxilla, the thumb ; the teeth, the :fingers. The lower Jaw represents the legs of the head; the teeth the toes. and, of all imaginable hypotheses, the styloid processes are th; sacrum of the head ! Reasons, worthy of the name, for these identifications are not to be found in the "Programm." Oken, having assumed once for all, that, as the brain-case repeats the spinal canal, the facial bones must repeat the other appendages of a vertebral column and the limbs, seems to have troubled himself no further about demonstration. What a bone should be, in order to fit plausibly into his scheme, that it was at once settled to bean appeal to the "idea" dispersing all doubts. A few years later Oken modified his original conception so far as to regard the nasal apparatus as a fourth vertebra. "\Vhatever may be thought about the more speculative passages of the extract above cited from Oken's work, and of bis a priori conception of what a skull must be, it contains ample evidence that he did, a posteriori and inductively, demonstrate the segmented character of the bony brain-case; and had nothing more ever been written on the subject, this great truth would have remained as a splendid contribution to morphology. But Oken greatly amplified the observational basis of his own doctrine; Spix took it up, in a modified form, and worked it out, in his own way, through the series of the Vertebrata in his great illustrated "Oephalogenesis," published in 1815; Bojanus did the like in the pages of the "Isis," and in the "Parergon " of his splendid monograph, the "Ana tome Testudinis ;" and, finally, C. G. Carns developed the doctrine, as far as it could well go, both a priori and a posteriori, in his " u rtheilen des Knochen und Schalen-Germ;;tes," published in 1828; in which, under the names of "Grund-form'' and "Schema," we have, among other things, "archetypal" diagrams of the Vertebrata generally, and of each vertebrate class. Under these circuinstances, the following passage, extracted |