Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/482

464 REPTILES [ANATOMY. groove shows serial enlargements corresponding with the successive portions of the adult brain, while the medullary plates close over the medullary groove and convert it into a canal which ultimately persists as the central canal of the spinal cord and the ventricles into which that canal opens anteriorly. The eyes arise as outgrowths from the brain aided and modified by ingrowths from the surface of the embryo. The ears and nasal organs arise mainly from supsrficial ingrowths. From the tissue on either side of the notochord and medullary groove are gradually formed the axial skeleton of the trunk and the muscles and other structures adjacent to it. The sides of the medullary plates bend down on either side and form the ventral laminae which split longitudinally, or they descend the inner layer joining with its fellow of the opposite side to form the alimentary tube. The two outer layers form the lateral walls of the trunk, the space between the two inner and the two outer layers constituting the first condition of what is subsequently the first peritoneal cavity. The limbs first appear as outgrowths from the external layers of the ventral laminae, but no rudiment of the limbs seems ever to be developed in the apodal Ophidians. On each side of that region which subsequently becomes the head and neck a series of perforations successively appear, and for the most part disappear, known as the visceral clefts, while their intervals are known as the visceral arches. The only visceral cleft which ever per- sists in the Reptilia is that which becomes the passage from the inner end of the Eustachian tube to the outer surface of the tympanic cavity. The foundations of the skull are laid in a cartilaginous investment of the anterior end of the notochord and of the incipient membranous labyrinth, whence two columnar prolongations, the tra- beculae, pass forwards on either side of the support of the pituitary body. We have seen the persistent nature of these trabeculaj in the cranium of Ophidians. The central part of the facial region of the skull is formed by a car- tilaginous ethmoidal process at the anterior end of the trabecule. Hence and from the side of the auditory cartilage cartilaginous processes go forth which lay the foundation of the jaws, palatine structures, and hyoid apparatus. The circulating system in its earliest condition is very different from that which ultimately exists. At first the heart is not a tubular structure, but it gradually folds and subdivides itself. The arteries proceeding from it (and the veins converging to it) at first follow the general course of the arteries (and veins) of Fishes and aquatic breathing Amphibians. The arteries ascend within the visceral arches to meet in a dorsal aorta, as they must needs do in the animals just mentioned, seeing that in them it is the visceral arches which become the gill-bearing structures wherein alone the blood is aerated. The urinary organs are at first represented by Wolffian bodies only, which are formed from beneath the dorsal region of the body cavity, but subsequently, as has been mentioned, they become replaced by the two kidneys. The sexual glands themselves arise in connexion with the Wolffian bodies. At a very early stage of development the embryo as it were sinks into the surface of the ovum, while a membrane arises on all sides of it meeting dorsally over it, consti- tuting the embryonic envelope known as the amnion. From the hind part of the abdominal region of the embryo there also grows forth a vesicle which, becoming greatly enlarged and richly supplied with blood-vessels, spreads itself out on all sides just within the egg shell, and serves as the organ of respiration for the embryo. This directly respiratory structure is the allantois. The ventral surface of the embryo remains long open and connected with the ever-diminishing remains of the food yolk. As this ventral surface closes in, the remains of the yolk or vitellus become connected with the alimentary canal, but ly a very narrow tube called the vitelline duct. Before the process of development is complete, however, the last remains of the yolk become absorbed and taken up, and * the abdominal wall is finally closed. Space does not here allow of more than this brief indication of some of the leading facts of bodily development. "We cannot attempt to describe the complex processes of ossification by which the first foundations of the skeleton, and especially of the skull, become differentiated into its manifold component bones. For an account of this process, and of all the other details of embryonic development, the reader is referred to the valuable treatises to be found enumerated in the following list of herpetological works. GENERAL WORKS ON THE ANATOMY OF REITILES. Cuvier, Lecons d'Anat. Comp., 2d ed., Paris, 1835; Meckel, System d. Vergl. Anal., Halle, 1821; Dumdiil and liibron, Erpe'tologie Generate, Paris, 1834-54; Joh. Miiller, " Beitriigc zur Anat. u. Karurgcsfh. d. Ampliibicn, ' in Ztschr. f. Physiologic, vol. iv. pt. 2. 1 ^'2; Rymer Jones, art. "Reptilia," in Todd's Cyclopxdia, vol. iv., 1852; Staniiiiis, Amphibian, Devlin, 1856; Owen, Anatomy of Vertebrates, vol. i., 1866; Huxley, Anatomy of Vertebrate Animals, 1871; C. K. Hoffmann, in Bronn's Thierreich, vol. vi., div. 3; Gegenbaur, Grundrifs d. Vergl. Anat., 2d ed., 1877 (Eng. tr., Elements of Comparative Anatomy, 1878). OSTEOLOGY. Cuvier, Ossemens Fossiles, 4th ed., Paris, 1834; De Blainville, Osteographie Crocodilus, <fec., 1855; K. Hnllmann, Vergl. Osteolog. des Schld- fenbeins, 1837 ; Rbstlin, Der Ilau des knochemen Kopfes, StJttgart, 1844 ; Giebel, "Skeletd. Kvokodile," in Giebel's Ztsch. f. d. Ges. Naturw., 1877; Klein, "Skull of Crocodile," in Jahreshefte d. Vereins fur Vaterl. Naturk. in Wiirttemberg, 19ter Jahvg.; Pavker, Shoulder Girdle of Vertebrates, Ray Society, 1868 ; Id., " Skull of Lacertilia," Phil. Trans., vol. clxx., 1879; Id., "Skull of Snake," Phil. Trans., vol. clxix., pt. 2, 1878 ; Id., "Skull of Turtle," Proc. Hoy. Soc., vol. xxviii., 1879, and Challenger Reports, vol. i., 1880; Id., "Skull of Chamscleo," Trans. Zoo}. Soc., vol. xi., 18SO ; B. Balfour, "Skull of Mecistops," Proc. Zool. Soc., 1857, p.57, pi. 25 ; C. Gegenbaur, Untersuch. z. Vergl. Anat. d. Wirbelthiere (1 lift., " Carpus und Tarsus," 1864 ; 2 lift., " Schultergiirtel," 1865) ; Id., " Gliedmassen d. Wirbel- tliieve," in Aforph. Jahrb., ii., p. 397, 1876; If. FUvbringer, D. Knochen u. Alusteln v. d. schlangenahnlichen Sauriern, Leipsic, 1870; Id., Morph. Jahrb., i. p. 631, 1876 ; Gorski, Ueber das Becken der Saurier, Dorpat, 1852 ; C. H. IJrUlil, Skelet der Krokodiliner dargesteltt in SO Tafeln, 1862 ; C. Bora, " Cavpus und Tarsus d. Sauvier," in Morphol. Jahrb., ii., p. 1, 1870; H. Steckev, "Carpus und Tarsus v. Chameleon." in Sitzb. d. Kaiserl. Akad. d. Wis- sensch. Wien, Ixxv., 1 Abth., 1877; P. Albrccht, " Dinosauvia," in Hull, du Mus. Roy. dllist. Nat. de Belgique, 1883-84; P. Gevvais, " Ostdol. du Sphargis," in Nouv. Archives du Mas., 1872, viii. ; C. K. Hoffmann, " Beitvage z. Kenntniss d. Beckens bei den Reptilicn," in Niederl. Archiv f. Zool., iii., 1876 ; H. Rathke, Ueber d. Ban u. Entwickl. d. Brustbeins d. Saurier, 1854 ; W. Peters, "On the Ear Bones," in Monatsb. d. Konigl. Preuss. Akad. d. Wissench. z. Berlin, 1868-69-70-74 ; Huxley, " Ear Bones," in Proc. Zool. Soc., I860, p. 391 ; Id., "Dinosauria," in Quart. Jour. Geol. Soc., July 1870; Id., " Archceopteryx," Proc. Roy. Soc., No. 98, ISC ; Id., "Malleus and Incus," Proc. Geol. Soc., 1869, 391; Owen, A History of British Fossil Reptiles, 1849; Id., "Carapace and Plastron of Chelonians," Phil. Trans., 1849, pt. 1 ; Id., Pterodactyles (volume of Palteontp- praphieal Society for 1869); Id., Catalogue of Fossil Reptilia of S. Africa in Brit. Mus., 1876; Id., "Tympanum and Palate of Crocodilia," Phil. Trans., 1850 ; Id., " Archseoptevyx," Phil. Trans., 1863 ; Id., " Permian Theriodonts," Quart. Jour. Geol. Soc., August 1876; " Mosasauridx," ibid., Nov. 1877 ; Id., " Cynodraco," ibid.. May 1876 ; Id., "Dinosaurian Vertebra;," ibid., July 1876; H. Seeley, " Limb of Ophthalmosaurus," Quart. Jour. Geol. Soc., Dec. 1874; Id., " Plesiosauvian Pectoral Arch," ibid., Nov. 1874; Id.. "Chelonians," Ann. and Mag. Nat. Hist., Oct. 1871; Id., "On Dimorphodon," ibid., Oct. 1871; A. Gaudvy, "Permian Reptiles," in Bull. Soc. Geol. France. 3 ser., vii. p. 62, 1873; Cope, "Extinct Reptilia," Trans. Amer. Phil. Soc., 1868-69; Id., " Homologies of Cranial Bones of Reptilia," B. Nat. Hist., p. 194; Vogt, " Avchaeoptevyx," Rev. Sci., ser. 2, ix. p. 241, 1879; 0. C. Marsh, " Mosasauroid Reptiles," Amer. Jour. Sci. and Art, vol. iii., 1872, and vol. xix., Jan. 18SO ; Id., "Ptcvosauria," ibid., April 1872 ; Id., "Dinosaurs," Und., vol. xvi., Nov. 1878, vol. xvii., Jan. 1879, vol. xix., March and May 1880, and vol. xxi., July 1881. MYOLOGY. H. Buttmann. De Musculis Crocodili (Diss. Inaug.), Halle, 1826 ; S. Haughton, " Muscles of Crocodile," Proc. Roy. Irish Acad., vol. ix., 1866 ; G. Rolleston, "Shoulder Muscles," Trans. Linn. Soc., vol. xxvi. p. 009, 1868; N. Furbrineer, D. Knochen 11. Muskeln v. d. schlangenahnlichen Sauriern, Leipsic, 1870; Id., Morph. Jahrb., i. p. 631, 1876; Hans Gadow, " Bauchmuskcln d. Kvokodile," Aforphol. Jahrb., vii. p. 67; Gorski, Ueber das Becken der Saurier, Dorpnt, 1852 ; St G. Mivart, "Muscles of Iguana," in Proc. Zool. Soc., 1867, p. 766; Id., "Muscles of Chamseleo," in Proc. Zool. Soc., 1870, p. 850; A. Sanders, "Muscles of Platydactylus," in Proc. Zool. Soc., 1870, p. 413; Id., " Muscles of Liolepis," in Proc. Zool. Soc n 1872, p. 154 ; Id., " Sluscles of Pteryo- sauva," Proc. Zool. Soc., 1874, p. 71 ; Humphrey, " Muscles of Pscudopus," i" Jour, of Anat. and Physiol., vol. vi., 1872. VISCEHAL ANATOMY. Ilulke, " Retina of Reptiles," Jour. A nat. and PJitifioL, vol. i., 1867; C. Stewart, " Lacrymal Gland of Turtle," Monthly Microsc. Jotir., 1877, p. 241; M. Braun, " Urogenitnl System d. einheimischen Reptilien," in Arbeit en und Zool. Jour. Inst. Wurzburg. iv. 113-228. 1877; Briioke, " Me- chanik d. Kreislaufes b. d. S<-hildkroten," (iitzb. der Kaiserl. Akad. d, Wissensch. Wien, 416, 1850 ; Id., Denkschrift d. Wiener Akad., Iii., 1852, p. 335 ; G. I-'iitsch, "Amphibienherzen," in Rcirhert und Dubois Reymond's Archiv, p. i!54, 1869 ; Jacquart, " Coeur de la Tortue," Ann. des Sc. Nat., 4th sev., vol. xvi. p. 303, 1861; J. Miiller, "Die Lymphherzen der Schildkroten," in Abhandl. d. Kb'nigl. Akad. d. Wissensch. z. Berlin, 1839, p. 31 ; M. Braun, " Ban u. Entwick. Physiol. ; P. Gervais, "Dents de I'HclodeiTncs et des Ophidiens," in Archiir* <l. Zool. Experim., 1873, pi. 6; Ch. S. Minot, "Studies on the Tongue of Rcptil.-s and Birds," in Annivers. Mem. Boston Soc. Nat. Hist.. 1880 ; Bischoff, " Bau des Crocodilherzens," in Muller's Archir, 1836; G. Fritsch, "Verglcich. Anar. d. Amphibienherzen," in Reichert und Dubois Reymond's Archiv, 1869; C. S. Tomes, "Development of Teeth in Reptiles," Proc. Roy. Soc., vol. xxiii. p. 93 ; Id., Phil. Trans., vol. clxv., pt. 1; Id., ibid., vol. clxvi., pt. 2. NERVOUS SYSTEM AND ORGANS OF SENSE. R. Ruckherd, " Ccntralnerven- Bystem d. Alligators," in Ztsch. f. Wissensch. Zool., xxx. p. 336, 1878; C. Vogt, " Neurologic d. Reptilien," in Neue Denkschr. d. AUgem. Schweiz. Gesellsch. f. d. Gesammten Wissensc>,aften, xiv., Neuohfttel, 1840 ; J. G. Fischer, Gehirnnerven d. Saurier, Hamburg, 1852; St G. Mivart and R. Clarke, " Sacralplexus of Lizards," &c., in Trans. Linn. Soc., 2d ser.. Zool., vol. i., 1877 ;