Page:The American Cyclopædia (1879) Volume XIII.djvu/438

 PHILOSOPHICAL ANATOMY tific world in matters of philosophical anato- my. Oarus maintains that the same relation exists between the three cranial vertebras and the three cerebral masses pertaining to the three great sensorial nerves (of hearing, vision, and smell), as between each spinal vertebra and the ganglionic swelling of the cord which it envelops. He gave the name of dermatoskel- eton to that which in solidifying separates an animal from the external elementary substance, air or water; this external elementary sub- stance also penetrates within the animal, re- quiring a more or less solid limitation internal- ly, in the alimentary and respiratory systems, constituting the splanchnoskeleton ; the neuro- skeleton is that which limits and protects the nervous system, being peculiar to the verte- brates, the most perfectly developed, and in proportion to the nervous system. The der- matoskeleton is the first and lowest in the ani- mal kingdom ; it appears as horny envelope, shell, scales, osseous plates, and skin ; it is in- creased from without, permanent or deciduous, and reproduced by the coagulation or calcifica- tion of the integument. The splanchnoskele- ton is also inferior in rank, cartilaginous, but capable of undergoing bony transformation in the higher animals ; tracheal rings, branchial arches, and teeth belong to this skeleton ; the neuroskeleton is formed as indicated in the article BONE. He divides the cerebral mass into three portions, cerebellum, cerebrum, and optic lobes between them, with three pairs of ganglia in front ; the spinal ganglia, in man, are 30. H constructs the skeleton on geo- metrical principles, starting from the hollow sphere, double cone, and cylinder ; he makes what he calls proto-, deuto-, and trito-verte- brae ; the first (ribs) enveloping the body and its viscera in relation with vegetative life ; the second (vertebras) protecting the nervous sys- tem ; and the third (limbs) becoming the osse- ous framework which sustains the muscular and locomotive organs. His three principal cranial vertebrae correspond to the three cere- bral masses, and are the occipital, centricipital, and sincipital ; the three facial vertebrae form the nose and its cartilages, and the three inter- vertebra he names auditive, optic, and olfac- tory. But it has been found impossible to ex- plain the vertebrate homologies by his diagram archetype ; for this the reader is referred to the work above cited. In fishes we find the first development of the neuroskeleton, as dis- tinguished from the splanchnic and external skeletons, but at its lowest stage, being carti- laginous or partially osseous ; it is of inferior vitality, and the component parts are imper- fect in form and number; in this class the sexual organs predominate. In reptiles the neuroskeleton is for the first time bony ; the splanchnic skeleton is truly cartilaginous, and the external truly corneous ; the abdominal re- gion or the digestive system predominates. In birds the thoracic region or respiratory system predominates, extending even into the caVities of the bones and feathers. In mammals the cranium predominates and the nervous sys- tem, the neuroskeleton being the highest de- veloped with a corresponding inferiority of the external and splanchnic skeletons. Carus divi- ded the vertebrae into six portions, and the skeleton generally into this number or its mul- tiples, while Oken adopted the number five. Meckel did not materially affect the progress of philosophical anatomy, but he confirmed many previous principles and homologies by his mi- nute and accurate descriptions, his knowledge of individual formations, and his history of de- velopment. Prof. Owen has given the great- est extension to the science of philosophical anatomy in various writings and lectures since 1838, among which may be mentioned his vari- ous "Hunterian Lectures," "Lectures on Com- parative Anatomy," " On the Archetype of the Skeleton,"* "On the Nature of Limbs," and " On the Principal Forms of the Skeleton and Teeth;" the last is the most popular, and has been reprinted from "Orr's Circle of Sciences" at Philadelphia (12mo, 1854). As far as the skeleton is concerned, the aim of philosophical anatomy is to discover the original idea which presided at its construction, or the archetype to which all the modifications of the verte- brate series can be referred. The archetype refers principally to the neuroskeleton, which alone appears to have any typical pattern ; be- sides the other skeletons already defined by Carus, of which good examples (of the derma- toskeleton) may be found in the plates of the sturgeon, crocodile, and armadillo, and the carapace of the tortoise, he mentions a sclero- skeleton, or bones developed in tendons, liga- ments, and aponeuroses. His typical vertebra is here given : - Neural spine. Neurapophysis. Pleurapophysis. """* Haemapophysis. ~ Haemal spine. In the above figure the names printed in Eo- man letters are the autogenous elements, or those which are ordinarily developed from dis- tinct and independent centres; the names in Italics indicate the processes which are con- tinuations of some of the preceding elements the latter are the diapophyses or superior transverse processes, and the zygapopliyses 01 oblique articular processes of human anatomy. ZygapopJiysis. Diapophi/sis .... Parapophysis . . . '" Zygapophysis. . ...'*