Page:The American Cyclopædia (1879) Volume V.djvu/190

 186 COMPARATIVE ANATOMY years he had collected an immense amount of facts and materials, which are partly embod- ied in this book ; it is a monument of patient industry, a model in arrangement, and a mine of knowledge of which all observers since have availed themselves ; many of its unavoidable deficiencies have been supplied by later writers, especially by Meckel ; in it are laid down not only the analogies, but the differences in the structure of organized beings. His Ossemens fossiles, published in the first quarter of the century, is invaluable for its scientific and minute descriptions of the bones and teeth of extinct and living vertebrates. Contemporary with Cuvier was Geoffroy Saint-Hilaire, whose writings on comparative and philosophic anat- omy gave great impetus to the study of natural history. At the head of the German school of philosophical anatomy stands Lorenz Oken, who extended to natural science the principles which Kant had applied to mental and moral science. In 1802 he divided the animal kingdom into five classes, according to the predominance of the special senses ; in 1805 he maintained that all organic beings originate from and consist of cells; in 1806, while walking in the Hartz forest, he picked up the blanched skull of a roebuck, and, after contemplating the partially separated bones, exclaimed : " It is a vertebral column ! " In the following year he delivered the famous discourse on the " Signification of the Bones of the Skull," renewing the idea of the cranial and vertebral homologies, which has since been modified, extended, and perfect- ed by Richard Owen. Cams, in his " Treatise on Comparative Anatomy," of which the sec- ond edition was published in 1834, devotes about half to philosophical anatomy and the geometrical construction of the skeleton, carry- ing out the idea of Oken, Saint-Hilaire, and Spix, that the whole bony fabric is nothing but a vertebra repeated. According to Oken, the head is a repetition of the whole trunk, with all its systems. Cuvier ridiculed the idea of these transcendental homologies, and at his death the vertebral theory of the skull had apparently fallen into oblivion. In Owen's " Archetype and Homologies of the Vertebrate Skeleton," this theory is briefly stated as fol- lows : " The head is not a virtual equivalent of the trunk, but is only a portion, i. e., certain modified segments, of the whole body. The jaws are the 'haemal arches' of the first two segments; they are not limbs of the head." The head is not a repetition of all the rest of the body ; the skull is a region in itself, con- sisting of a series of segments or vertebrae es- sentially the same as those constituting the rest of the skeleton. The endoskeleton of the cranium, according to Owen, consists of the occipital, parietal, frontal, and nasal vertebrae ; the ribs of the first are the shoulder blades, and the divergent appendages of the anterior extremities ; the divergent appendages of the second are the branchiostegal rays, of the third the operculum, of the fourth the pterygoid and COMPASS the zygoma. The different modifications of the type skeleton will be treated in the article PHILOSOPHICAL ANATOMY. Owen revived and reworked the idea of Oken, and brought it to the now generally admitted segmental consti- tution of the vertebrate skeleton, as fully illus- trated in the above mentioned work. COMPASS, a magnetized needle, balanced upon its centre so as to swing freely, used to indicate the magnetic meridian, and, by means of a graduated circle connected with it, the azimuths or bearings of objects from this meridian. The Chinese appear to have been acquainted with the property of polarity in the loadstone, and in iron or steel magnetized by it, and to have been the first to apply this. Some affirm that they employed only, the loadstone (magnetic iron ore), floating it upon a piece of cork ; and that the magnetized needle is the invention of Flavio Gioja of Amalfi, who lived in the early part of the 14th century. Dr. Gilbert, in his De Magnete, &c. (London, 1600), states that Mariner's Compass. the compass was brought to Italy from China by Marco Polo about 1295. But there is evi- dence of its having been used in France about the year 1150, in Syria about the same period, and in Norway previous to 1266. Several forms of the compass are in use. The mari- ner's, made for service at sea, and especially for indicating the direction in which the ship's head points, consists of a needle attached to the under side of a circular card or disk, upon the top of which the cardinal points and their subdivisions are marked. A fleur de lis is on the N. pole of the needle, and the letter S. on the opposite pole. E. and W. are placed, the one to be toward the east, and the other toward the west, when the card, swinging with the needle, comes to rest, dividing the circle into quadrants. A diameter is drawn, bisecting each of these, fixing the N. E., S. W., N. W., and S. E. points upon the circumference ; and the arcs thus obtained are again bisected by