On the archetype and homologies of the vertebrate skeleton / by Richard Owen.
- Richard Owen
- Date:
- 1848
Licence: Public Domain Mark
Credit: On the archetype and homologies of the vertebrate skeleton / by Richard Owen. Source: Wellcome Collection.
Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.
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![‘ pisifonne(/;);' the bone u represents a small ‘ magnum' and ‘ uncilorme.’ In the tai-sus, ossification extends from the astragalo-naviciilar bone asc, and takes the place also of the internal and middle cuneiform bones. There is an external cuneiform bone, and a single bone b supports the two outer toes, and represents both divisions of the ‘ cuboides’in the Chelonia. In some Saurians the calcaneum retains its true or theoretical character, the articular portion (fig. 3, cl) being distinct from the fulcral or sesamoid portion (cl'). In the dog and other carnivora, and in the wombat, the scaphoid is con- nate with the lunare ; three carpal bones in the wrist of the orang are here therefore represented by one. In the hind-foot of the rhinoceros (fig. 17) the internal cuneiforine is gone, together with the digit it would have sup- ported. In the ruminant the cuboid has coalesced with the navicular (fig. 18, bs). In the horse the external cuneiform (fig. 19, ce) is the largest of the distal row corresponding with the enormous toe which it supports; and the navicular, s, remains distinct from the cuneiform, b, which we may sup- pose to be represented by that portion which in the Emys supports the fourth toe. In the ruminant the fibula is reduced to a small ossicle (fig. 18, or), repre- senting its distal end, wedged between the tibia and the calcaneum : the ulna is almost as much reduced in the fore-limb, and is commonly anchylosed to the radius. The two metacarpals of the principal digits, iii and iv, coalesce to form the single cannon-bone, and the two corresponding metatarsals are subject to a like coalescence (fig. 18), a single bone supporting the fully developed toes, as in the bird : the rudimental back-toes, ii and v, have small detached metatarsals when they exist. Whilst the number of toes is thus seen to fall short, progressively, of five, the typical character of that num- ber is still indicated by the power of determining the particular toe or toes of the five in man, which are retained in the tetradactyle, tridactyle, didactyle and monodactyle feet respectively of the lower mammals. But although the number ‘five’ thus governs the development of digits, properly so called, in all existing air-breathing vertebrate, the tendency to multiplication of terminal rays in the diverging appendages developed for locomotion may be seen to manifest itself in the sexual ‘spurs’ of the Gallmacea and Monotremes-, in the hereditary supernumerary toes in certain varieties of the common fowl, and even in some individuals of the human race. But the single spur of the tetradactyle cock is not more a homologue of a normal digit in a penta- dactyle reptile or mammal, than is the spur of the Platypus, or the second spur in the Pavo bicalcaratus. Having thus noticed some of the chief varieties of the mammalian modifi- cation of the vertebrate archetype, there remains to add only a few words in explanation of fig. 6,—the diagram of the human skeleton. As this is that which the anatomist has been accustomed to hear described most frequently and exclusively by the special terms, and according to the special views and ends of anthropotomy, the language in which its deviations from the common archetype have now to be noticed will probably appear strange and bizarre. The comprehension of the explanation wall be facili- tated by reference to the special name of the bone through its numeral in the column of names whenever such bone is alluded to under its general or archetypal name. In the first and, notwithstanding the upright posture, the most anterior of the cranial segments, by reason of their forward curvature, the haem- apophysis (21) coalesces early with its own moiety of the divided spine (22), and the same thing happens to the next haemal arch (20) with subsequent oblite- ration of the .“ympliysis between the halves of its s])ine (32). o](https://iiif.wellcomecollection.org/image/b21307830_0219.jp2/full/800%2C/0/default.jpg)
