Page:The American Cyclopædia (1879) Volume XVI.djvu/345

 VERTEBRA VERTIGO 325 stitutional provisions of February, 1875, made Versailles the legal capital, though it is prac- tically only the seat of the senate and assem- bly, which occupy chambers in the palace. VERTEBRA. See SKELETON. VERTEBRATA, a name applied by Lamarck to the highest branch of the animal kingdom, from its being characterized by a bony or cartilaginous internal skeleton, of which the most essential and persistent portion is the vertebral column or spine. (See COMPARA- TIVE ANATOMY, PHILOSOPHICAL ANATOMY, and SKELETON.) Aristotle had made the distinction of ivatfia (blood animals) and avai/ia (bloodless animals), corresponding respectively to the ver- tebrata and invertebrata of Lamarck. Oken called the vertebrates sarcozoa or flesh ani- mals ; Ehrenberg, myeloneura ; De Blainville, osteozoaria; audOw&i,myelencephala. These various terms describe very accurately the re- lations of the skeleton, red blood, muscles, and cerebro-spinal nervous centres, character- istic of fishes, batrachians, reptiles, birds, and mammals. The essential character of the spi- nal column is to have a distinct cavity above the axis for the nervous centres, and another below for the organs of vegetative life, both circumscribed by complicated bony arches. Vertebrates are the doubly symmetrical type of Von Baer, their embryological development producing identical parts arising on both sides of an axis, growing upward and downward and shutting up along two lines, the inner lay- er of the germ being enclosed below and the upper above ; Van Beneden calls them hypoco- tyledones or hypovitellians, from the vitellus or yolk entering the body from the under or ventral side. Lamarck also styles them intel- ligent animals, but comparative psychology is not sufficiently advanced to enable us to dis- tinguish in this way between the sensations of a fish and a cephalopod or an insect. In vertebrates reproduction is sexual, without normal hermaphroditism, and the jaws move vertically and not laterally. Ehrenberg di- vides vertebrates into nutrientia, or warm- blooded, and taking care of their young, like mammals and birds; and orphanozoa, cold- blooded, taking no care of their young, like reptiles and fishes ; but some of the latter do take care of their young, in a different or in the same way as the former division. The classes of vertebrates, according to Agassiz, are : 1, myzonts (myxinoids and cyclostomes) ; 2, fishes proper ; 3, ganoids (sturgeons, &c.) ; 4, selachians (sharks and rays) ; 5, amphibians (frogs, salamanders, &c.) ; 6, reptiles ; 7, birds ; and 8, mammals. In this type, to use his words ("Atlantic Monthly," January, 1862, p. 12), " the head is the prominent feature ; it is, as it were, the loaded end of the longitudinal axis, so charged with vitality as to form an intelligent brain, and rising in man to such predominance as to command and control the whole organism." The classification adopted by Prof. Owen is as follows: I., piaces, with the subclasses dermopteri (cirroatomi, cyclosto- mi), teleostomi (malacopteri, anacanthini, acan- thopteri, plectognathi, lopholranchii, ganoidei), plagiostomi (holocephali, plagiostomi), andjm>- topteri (lepidosiren) ; II., amphibia, with the orders ophiomorpha, ichthyomorpha, theriomor- pha, and labyrinthodontia ; III., reptilia, with the orders chelonia, lacertilia, ophidia, croco- dilia, and the extinct ichlhyopterygia, sauro- pterygia, anomodontia, dinosauria, and ptero- sauria; IV., aves, divided into the three sec- tions of altrices (embracing the raptores, scan- sores, volitores, and cantores), prcecoces (rasores, curaores, grallatores, natatores), and uroioni (archseopteryx) ; V., mammalia, with the four subclasses of archencephala (Mmana), gyren- cephala (quadrumana, carnivora, artiodactyla, perissodactyla, proloscidia, toxodontia, airenia, cetacea), lissencephala (bruta, cheiroptera, in- sectivora, rodentia), and lyencephala (marsu- pialia,monotremata). Huxley makes the ver- tebrata his sixth subkingdom, characterized by the body composed of definite segments ar- ranged longitudinally or one behind the other. The main masses of the nervous system are on the dorsal aspect, and are completely shut off from the general body cavity. The limbs, when present, are turned away from that side of the body on which the main nervous masses are situated, and are never more than four. He divides the vertebrata into three primary provinces, viz. : ichthyopaida (fishes and am- phibians), sauropsida (reptiles and birds), and mammalia. His classes are the following: I., pisces, with the orders pharyngolranehii, marsipobrancMi, teleostei, ganoidei, elasmo- branchii, and dipnoi; II., amphibia, with the orders urodela, labyrinthodontia, gymnophiona, and anoura ; III., reptilia, with the orders chelonia, lacertilia, ophidia, crocodilia, plesio- sauria, ichthyosauria, dicynodontia, ornitho- scelida, and pterosauria; IV., aves, with the groups ratitcB (with the sternum devoid of a keel), carinatcs (sternum provided with a keel), and saururce; V., mammalia, with the groups ornithodelphia (monotremata), didelphia (mar- supialia), and monodelphia (edentata, vngula- ta, toxodontia, sirenia, cetacea, hyracoidea, proboscidea, carnivora, rodentia, insectivora, cheiroptera, and prima tea). For further details of his classification of birds, see ORNITHOLOGY. Modifications of these classes and orders are almost as numerous as the specialists who have investigated them, and chiefly of interest to students of the history of zoology. VERTIGO (Lat., from vertere, to turn), a com- mon symptom of cerebral disturbance, with or without obscurity of vision, in which objects appear to turn round ; besides the abnormal subjective sensations, there may be disordered movements prompted thereby. It may arise from too much or too little blood sent to the brain ; from poisons in the circulation, as in alcoholic and other intoxication ; and from lesions of the sensorial centres or the nerves therewith connected. The effect is that the