EQUID& 401 



understood. The larynx has the lateral sacculi well developed, 

 though entirely concealed within the alae of the thyroid cartilage. 

 The trachea divides into two bronchi, one for each lung. 



Nervous System, The brain differs little, except in details of 

 arrangement of convolutions, from that of other Ungulates. The 

 cerebral hemispheres are rather elongated and subcylindrical, the 

 olfactory lobes are large and project freely in front of the hemi- 

 spheres, and the greater part of the cerebellum is uncovered. The 

 eye is provided with a nictitating membrane or third eyelid, at the 

 base of which the ducts of the Harderian gland open. 



Reproductive System. The testes are situated in a distinct sessile 

 or slightly pedunculated scrotum, into which they descend from the 

 sixth to the tenth month after birth. The accessory generative 

 glands are the two vesiculse seminales, with the median third vesicle, 

 or uterus masculinus, lying between them, the single bilobed pro- 

 state, and a pair of globular Cowper's glands. The penis is large, 

 cylindrical, with a truncated, expanded, flattened termination. 

 When in a state of repose it is retracted by a muscle arising from 

 the sacrum, within the prepuce, a cutaneous fold attached below the 

 symphysis pubis. 



The uterus is bicornuate. The vagina is often partially divided 

 by a membraneous septum or hymen. The mammse (as in other 

 members of the suborder), are two, inguinally placed. The surface of 

 the chorion is covered evenly with minute villi, constituting a diffuse 

 non-deciduate placenta. The period of gestation is eleven months. 



Bibliography. M. S. Arloing, " Organisation du pied chez le cheval," Ann. 

 Sci. Nat. 1867, viii. pp. 55-81 ; H. Burmeister, Los caballos fosiles de la Pampa 

 Argentina, Buenos Ayres, 1875 ; Chauveau and Arloing, Traite d'anatomie com- 

 paree des animaux domestiques, Paris, 1871, and English edition by G. Fleming, 

 1873 ; E. Cuyer and E. Alix, Le Cheval, 1886 ; A. Ecker, " Das Europaische Wild- 

 pferd und dessen Beziehungen zum domesticirten Pferd," Globus, Bd. xxxiv. 

 Brunswick, 1878 ; Forsyth-Major, " Beitrage zur Geschichte der fossilen Pferde 

 besonders Italiens," Abh. Schw. Pal. Ges. iv. pp. 1-16, pt. iv. ; George, " Etudes 

 zool. sur les Hemiones et quelques autres especes chevalines," Ann. Sci. Nat. 

 1869, xii. p. 5 ; E. F. Gurlt, Anatomische Abbildungen der Haussdugethiere, 1824, 

 and Hand, der vergleich. Anat. der Haiissaugethiere, 2 vols. 1822; Huet, " Croise- 

 ment des di verses especes du genre cheval," Nouv. Archives du Museum, 2d ser. 

 torn. ii. p. 46, 1879 ; Leisering, Atlas der Anatomic des Pferdcs, Leipsic, 1861 ; 

 J. M'Fadyean, The Anatomy of ihe Horse, 1884 ; 0. C. Marsh, " Notice of New 

 Equine Mammals from the Tertiary Formation," Am. Journ. of Science and Arts, 

 vol. vii. March 1874; Id. "Fossil Horses in America," Amer. Naturalist, vol. 

 viii. May 1874 ; Id. " Polydactyle Horses," Am. Journ. of Science and Arts, vol. 

 xvii. June 1879 ; Franz Miiller, Lehrbuch der Anatomic desPferdes, Vienna, 1853 ; 

 R. Owen, "Equine Remains in Cavern of Bruniquel," Phil. Trans, vol. clix. 

 (1870), p. 535 ; W. Percivall, The Anatomy of the Horse, 1832 ; G. Stubbs, 

 Anatomy of the Horse, 1766. F. H. Huth's Bibliographical Record of Hippology 

 (1887) contains a list of nearly four thousand works on Horses and Equitation, 

 published in the various languages of the civilised world. 



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