is connected to the symphysis pubis by means of a strong triangular fascia, the ligamentum suspensorium penis.'

The corpus cavernosum' is composed of a cellular structure enclosed in a strong sclerous tunic, from the inner surface of which are given off numerous bands, trabeculæ,' which converge towards the middle line of the inferior wall; they are most abundant in the middle line of the organ, where they form a septum between the two lateral halves of the corpus cavernosum: but this becomes incomplete or pectinate' anteriorly. The so-called cellular structure of the corpus cavernosum consists of a plexus of dilated and freely intercommunicating veins, the interspaces of which are occupied by contractile tissue: the fibres being unstriped and with a general arrangement transversely to the axis of the penis.

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Besides the erectores penis' and 'acceleratores urinæ,' there is a remnant of the levatores penis' reduced to the function of compressores venæ dorsalis ;' and occasionally a small fan-shaped muscle, ischio-bulbosus,' may be defined in the interspace between the bulb and crura penis, having a slender attachment to each ischium, and expanding upon the bulb. The prepuce is connected to the glans on its under part by means of a narrow fold, with some sclerous tissue, termed the 'frænum præputii.' At the base of the prepuce, where it is reflected over the glans, open the small lenticular representatives, called glandulæ odoriferæ,' of the preputial follicles of lower Mammals.

534

B. FEMALE ORGANS OF MAMMALS.

The ovaries retain, as in lower Vertebrates, their abdominal position; but are relatively small in Mammalia, and consist of a dense areolar 'stroma,' which, with the ovisacs therein developed, is inclosed in a firm sclerous 'tunica albuginea,' fig. 534, a. The abdominal aperture of the oviduct is wide, and, as a rule, fimbriate;' but the canal quickly contracts, usually to a diameter like that of the spermduct, and, after a certain course, suddenly Section of Human Ovarium; nat. size. expands, or opens, into a 'uterus.' This may remain distinct from its fellow; but a prevalent mammalian characteristic is a blending of the uteri, to terminate by one valvular orifice in a vagina;' the confluence extending, by degrees, in different species, until a single uterus results. The vagina, as a rule, is single, and usually

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terminates by a' vulva' distinct from the vent. The clitoris' is single. The variations in the efferent and subordinate parts of the female organs are greater and more numerous in Mammals than in other Vertebrates, and with female sexual organs are associated functional mammary glands: marsupial pouches are superadded in most Lyencephala.

§ 382. In Monotremata.-The female organs here consist of two ovaria, the right much smaller than the left, two oviducts, two uteri, an urogenital passage, and a clitoris.

The ovaria correspond in situation and surrounding attachments with the testes in the male; and the oviducts and uteri exhibit in their closely convoluted disposition an analogy with the spermducts.

The left ovary, fig. 535, f, is an irregular, semi-elliptical, flattened body, with a wrinkled and granulate surface in the unexcited state; but becomes thicker, with the surface studded by elevations formed by the ovisacs in different stages of development, at the season of sexual excitement. At this period usually two ovisacs, as in the figure, are conspicuously larger than the rest, and present each a diameter of about two lines. The right ovary, ƒ', is a narrow, thin, generally elongated body; sometimes broader, with a finely granulated surface. It is often scarcely to be distinguished from the ovarian ligament to which it is attached. This ligament, i, i, arises from the posterior parietes of the abdomen, behind and a little on the outer side of the kidney, and passes along the edge of the broad ligament to the fallopian extremity of the oviduct, where it divides into two; one portion is attached to the side of the ovary, the other to the posterior margin of the fallopian orifice: after a course of an inch they again unite, and the ligament is continued along the anterior part of the uterus to its cervix, where it is insensibly lost. The two separated portions of the ligament support a large pouch of peritoneum, which forms the ovarian capsule; the wide anterior orifice of the oviduct is also, by means of this ligament, prevented from being drawn away from the ovary.

The efferent canal of the ovarian products is divisible into an oviduct or fallopian tube, d', and an uterus, d. The size of the latter is nearly equal on both sides, but the right oviduct is much shorter than the left, and corresponds with the abortive condition of the ovary. The external serous coat of the oviduct is loosely connected to the muscular coat by filamentary processes of areolar tissue, among which numerous tortuous vessels ramify. The muscular coat is thin and compact, and is most readily demonstrable

in the uterus. The mucous coat is thin and smooth in the oviduct; it is thick, soft, plicated, but not villous, in the uterus. The left uterus in a female with a large ovary, shot in the month of September, was two inches long, from four to five lines in diameter, and about a line thick in its parietes; it became suddenly contracted and thinner in its coats to form the oviduct, which presented a diameter of about two lines, slightly enlarging to within an inch of the extremity, which forms a wide membranous pouch, d' opening into the capsule of the ovary by an oblong orifice or slit, e, of eight lines in extent, The edges of this orifice were entire as in the oviducts of Reptiles, not indented as in the fimbriated extremity of the Fallopian tube in higher Mammals. The entire length of the oviduct and uterine tube, when detached from their connections with the mesometry, was nine inches. The right uterus and oviduct of the same specimen exhibited similar differences in diameter and structure, but was shorter, measuring only six inches in length.

The thickened parietes of the uterine tube depends chiefly on an increase of the inner membrane, which, at the cervix uteri, presents deep and close-set furrows: these, as the canal widens, are gradually lost, and the surface becomes more or less smooth. In the oviduct, the inner surface is smooth on leaving the uterus, then becomes finely reticulate, and in the terminal dilated part becomes again smooth. The cervix uteri makes a valvular projection analogous to an os tinca on each side of the commencement of the urogenital canal, just beyond the orifice of the urinary bladder. There are two orifices on each of these prominences: the lower one is the termination of the ureter-a bristle is represented as passing through it in fig. 535; the upper or anterior orifice is the os uteri, m. In young or virgin Ornithorhynchi this orifice forms scarcely any projection into the urogenital canal, and it is divided by a narrow septum. The urogenital canal, c, is one inch and a half long, and three or four lines in diameter, but capable of being dilated to as great an extent probably as the pelvis will admit of; the diameter of the bony passage being seven-tenths of an inch. It is invested with a muscular coat, the external fibres of which are longitudinal; the internal, circular. The inner membrane of this part is disposed in longitudinal rugæ more or less marked, but presents as little the character of a secreting membrane as that of the vestibule, being smooth and shining; the orifices of a few minute follicles are situated in the interstices of the ruga near the orifice of the urinary bladder.

The common vestibule, b, is about one inch four lines in length, and varies from half an inch to an inch in diameter: it is lined by a dark-coloured epithelium. The rectum opens freely into it posteriorly, as indicated by the probe b'. On the sternal aspect of the vestibule there are a series of longitudinal fibres, which extend from its external orifice to that of the urogenital cavity, the office of which is to approximate these orifices; and in this action certain oblique fibres assist, while at the same time they close the rectum.

On the sternal aspect of the urogenital canal, and close to where it joins the vestibule, the clitoris is situated, which is consequently about an inch and a half distant from the external orifice of the vestibule. It is inclosed in a sheath upwards of an inch in length, and about two lines in diameter, of a white fibrous texture, and with a smooth internal surface, and this sheath communicates with the vestibule about a line from the external aperture. The clitoris itself is a little flattened body shaped like a heart on playing cards; it is about three lines long, and two lines in diameter at its dilated extremity, where the mesial notch indicates its correspondence of form with the bifurcated penis of the male.

At the base of the clitoris are two small round flattened glands, the homotypes of Cowper's glands in the male, which open into the sheath or preputium clitoridis.

§ 383. In Marsupialia. In this order the female organs consist of two ovaries, two oviducts or fallopian tubes, two uteri, two vaginæ, an urogenital canal, and a clitoris.

The ovaries are small and simple in the uniparous Kangaroos, fig. 538, a, a; tuberculate and relatively larger in the multiparous Opossums, presenting the largest size and most complicated form in the Wombat, fig. 536. In Macropus they are lodged within the expanded orifice of the oviduct, or 'pavilion,' near the upper or anterior extremities of its two principal lobes. These are of considerable extent, and their internal surface, which is highly vascular, is beset with rugæ and papillæ. In the Dasyures and Petaurists the ovaries are elliptical, subcompressed, and smooth. In the Virginian Opossum the ovary consists of a lax stroma remarkable for the number of ovisacs imbedded in it, the largest of which are the most superficial, and give rise to the tubercular projections on the surface. In the Wombat, fig. 536, each ovary, besides being lodged in the pavilion, as in the Kangaroo, is inclosed with the pavilion in a. peritoneal capsule it is botryoidal in form, resembling the