EQUIDA 4ol 
understood. The larynx has the lateral sacculi well developed, 
though entirely concealed within the ale 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 vesicule 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 mamme (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. 8. Arloing, ‘Organisation du pied chez le cheval,” Ann. 
Set. Nat, 1867, viii. pp. 55-81; H. Burmeister, Los caballos fosiles de la Pumpu 
Argentina, Buenos Ayres, 1875; Chauveau and Arloing, Zratté d’anatomie com- 
parée des animaux domestiques, Paris, 1871, and English edition by G. Fleming, 
1873; E. Cuyer and E. Alix, Le Cheval, 1886; A. Ecker, ‘‘ Das Europiische Wild- 
pferd und dessen Beziehungen zum domesticirten Pferd,’ Globus, Bd. xxxiv. 
Brunswick, 1878 ; Forsyth-Major, ‘‘ Beitrage zur Geschichte der fossilen Pferde 
besonders Italiens,” 4h. Schw. Pal. Ges. iv. pp. 1-16, pt. iv.; George, “ Etudes 
zool. sur les Hémiones et quelques autres espéces chevalines,” Ann. Sci. Nat. 
1869, xii. p. 5; E. F. Gurlt, dnatomische Abbildungen der Hausscugethicre, 1824, 
and Hand. der vergleich, Anat. der Hausstiugethicre, 2 vols. 1822; Huet, ‘ Croise- 
ment des diverses espéces du genre cheval,” Nowv. Archives du Muséum, 2d sér. 
tom. ii. p. 46, 1879; Leisering, Atlas der Anatomie des Pferdes, Leipsic, 1861 ; 
J. M‘Fadyean, The Anatomy of the Horse, 1884; O. C. Marsh, ‘‘ Notice of New 
Equine Mammals from the Tertiary Formation,” din. Journ. of Science and Arts, 
vol. vii. March 1874; Id. ‘‘ Fossil Horses in America,” Amer. Naturalist, vol. 
viii. May 1874 ; Id. ‘‘ Polydactyle Horses,” lim. Journ. of Science and Arts, vol. 
xvii. June 1879 ; Franz Miiller, Lehrbuch der Anatomie des Pferdes, Vienna, 1853 ; 
R. Owen, ‘‘Equine Remains in Cavern of Bruniquel,” Phil. Trans. vol. clix. 
(1870), p. 585; 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. 
26 
