SOLIPEDA. 



743 



numerous small bundles. Arrived at the pos- 

 terior extremity of the testes, the epididymus 

 folds back upon itself, to constitute the vas 

 deferens ; which, at its commencement, is 

 very tortuous, and forms a protuberance of 

 considerable size (/). The vasa deferentia 

 (I, m, ?i) are upwards of fourteen inches in 

 length, and, during the greater part of their 

 course, about two lines in diameter ; but to- 

 wards their termination they become, for a 

 length of about seven inches, much dilated, 

 here measuring upwards of fifteen lines in 

 circumference (oo). The caliber of the in- 

 ternal canal does not, however, expand in 

 proportion to the dilatation of the exterior of 

 the duct. 



female Organs of Generation. The gene- 

 rative organs in the female solipeds offer no 

 variations of structure from the usual type 

 common to placental quadrupeds. The cli- 

 toris (Jig. 519. a) is of great size, and is 

 lodged in a cavity appropriated to its recep- 

 tion, situated immediately above the inferior 

 (i. e. anterior) commissure of the labia pudendi ; 

 its glans is enclosed in an ample prepuce, 

 above which may be observed an orifice leading 

 into a cavity big enough to lodge a small 

 bean. The canal of the vagina is about a foot 

 in length, and in its capacity corresponds with 

 the ample dimensions of the penis of the other 

 sex. 



Immediately behind the orifice of the ure- 

 thra, the mucous membrane of the vagina forms 

 a broad fold, which is directed forwards and 

 lies immediately over the urethral opening : 

 the length of this fold in the adult mare is 

 about eight inches, and, near its middle, it is 

 upwards of an inch in breadth. 



The urinary bladder is small in comparison 

 with the size of the animal ; its shape is nearlv 

 round; and its circumference, when moderately 

 distended, about a foot and a half. The urethra 

 is remarkably short and capacious, the circum- 

 ference of its canal being about three inches, 

 while its length is only about an inch and a 

 quarter. 



The orifice of the uterus (i) projects to the 

 distance of about half an inch into the upper 

 end of the vagina, and is of a rounded shape, 

 encircled by a thick margin. The womb is 

 made up of the body and two cornua, which 

 latter, in the unimpregnated state, measure 

 about seven inches in length. 



The ovaria and fallopian tubes present 

 nothing remarkable in their structure or ar- 

 rangement. 



Gravid Uterus. The anatomy of the con- 

 tents of the gravid uterus, and the arrange- 

 ment of the membranes that enclose the foetus 

 offer some peculiarities worthy of notice. 



The foetus in utero in the solipeds, is en- 

 veloped in the usual uterine membranes, 

 the amnion, the chorion, and the allantoid ; 

 but the disposition of these envelopes differs 

 remarkably from what exists in the rumi- 

 nants, and many other quadrupeds. 



The urachus (fig. 520. a) issues from the 

 umbilicus in company with the umbilical arte- 

 ries and vein (/), and, in the ovum represented 



in the figure, was found at some distance from 

 the umbilical opening to measure about five 

 inches in circumference, beyond which point 

 its diameter gradually diminishes, till it reaches 

 the point at which the amnion spreads out 

 on all sides to envelope the foetus, where it 

 terminates by the orifice <?, and is prolonged 

 to form the allantoid, which encompasses the 

 rest of the cord. On the arrival of the al- 

 lantoid at the extremity of the cord, it ex- 

 tends itself upon the chorion to which it be- 

 comes adherent, lining its internal surface in 

 such a manner, that the two seem to form but 

 a single membrane, the inner surface of which 

 is formed by the allantoid (g), its exterior by 

 the chorion (k). 



Fig. 519. 



Organs of generation and gravid uterus of the mare. 

 Vagina laid open. (After Daubenton.} 



a, the clitoris ; b, anus ; c, rectum ; d, posterior 

 surface of the vagina ; e, the orifice of the urethra ; 

 /, membrane which covers the urethral opening ; g, 

 the canal of the urethra ; h, the bladder ; i, i, the ure- 

 ters ; k. continuation of the vagina ; /, orifice of the 

 womb ; m, foetus as seen through the transparent 

 amnion, n ; o, portion of the umbilical cord that ex- 

 tends from the umbilicus of the foetus as far asp, the 

 point where the amnion spreads out ; q, portion of the 

 umbilical cord which extends beyond the amnion to 

 the point r, where the chorion and the allantoid 

 become united ; s, the allantoid ; t, the chorion seen 

 from its outer surface ; v, a hippomanes attached by 

 its pedicle ; x, y, chorion adherent to the uterine walls 

 by numerous rugse ; z, the left ovarium ; a', the sper- 

 matic vessels. 



The size of the umbilical cord gradually 

 enlarges as it approaches the chorion, owing 

 to the progressive dilatation of the vessels 



SB 4 



