termination of the spermducts is the homotype of the vagina some modification of this part might be anticipated in the male

503

Male organs.

corresponding with the extraordinary form and development which characterise the vagina in the female: accordingly we find that the prostatic tract of the urethra, ib. b, is proportionally longer and wider in the Marsupial than in any other Mammal. It swells out immediately beyond the neck of the bladder, and then gradually tapers to its junction with the spongy part of the urethra. Its walls are thick, formed by an external thin stratum of nearly transverse muscular fibres, and by a thick glandular layer, the secretion of which exudes by innumerable pores upon the lining membrane of this part of the urethra. In a male Kangaroo I found that a glairy mucus followed compression of this musculoprostatic tract of the urethra: the canal itself is but slightly dilated. Three pairs of Cowperian glands, ib. c, c, c, pour their secretion into the bulbous part of the urethra: the upper or proximal pair are not half the size of the two other pairs in the Kangaroo, but are relatively larger in the Koala and other Marsu

pials: the two lower pairs are situated, one on each side the lateral division, e, e, of the bulb of the urethra; their ducts meet and join, above this part, with the duct of the smaller gland: each

gland is enclosed by a muscular capsule. The penis consists of a cavernous and a spongy portion, each of which commences by two distinct bodies. The separate origin of each lateral half of the spongy body constitutes a double bulb of the urethra, ib. e, e, and the accelerator urinæ,' as it is termed, undergoes a similar division into two separate muscles, each of which is appropriated to compress its particular bulb. The two bulbous processes of the corpus spongiosum soon unite to surround the urethra, but again bifurcate to form a double glans penis in the multiparous Marsupials, in which most of the ova are impregnated in both ovaria, as e. g. in the Phalangers, Perameles, Opossums, &c., b, b, fig. 504. In the uniparous Marsupials, as the Kangaroo, the glans penis, fig. 503, f, is single.

The intermediate structures of the glans between the two extremes above instanced are presented by the Ursine Dasyure, Koala, and Wombat. In the Koala, fig. 503, B, the glans penis terminates in two semicircular lobes, and the urethra is continued by a bifurcated groove along the mesial surface of each lobe. In the Wombat, ib. C, there is a similar expansion of the urethra into two divergent terminal grooves, but the glans is larger, cylindrical, and partially divided into four lobes: the chief peculiarity in this part of the Wombat is the callous external membrane of the glans, and its armature of small recurved, scattered horny spines. The small retroverted papillæ on the infundibuliform glans of the Koala and on the bifurcate glans of the Phalangers and Petaurists are not horny. In the Perameles lagotis not only is the glans bifurcate, but each division is perforated, and the urethral canal is divided by a vertical septum for about half an inch before it reaches the forked glans: from the septum to the bladder the canal is simple, as in other Marsupials. The divisions of the glans in the Opossums, fig. 504, b, and Phalangers are simply grooved.

The corpus cavernosum penis commences by two crura, figs. 503, 504, d, d, neither of which have any immediate attachment to the pelvis. In the Kangaroo these crura, and the two bulbs of the corpus spongiosum, soon unite to form a single cylindrical body, the blended cavernous and spongy structures forming the parietes of a canal which nearly follows the direction of the axis of the penis, and contains or constitutes the urethra: a transverse section of the corpus cavernoso-spongiosum thus resembles a ring; but the lateral erectile tracts are separated by two vertical septa which extend from the central canal, the one to the dorsum penis, the other to the inferior wall: in this case there is no definite commencement of the glans penis; its termination is that of the

corpus cavernosum, the urethra, with a corpus spongiosum, projecting and opening beneath the apex. In Perameles, Didelphys, Phascolarctus, and Phascolomys, the corpus spongiosum maintains its character for a greater extent, and may be more distinctly recognised as forming the proper wall of the urethral canal, which sooner becomes superficial, and the glans penis is better defined. In the Kangaroo and Potoroo, the erectores penis,' fig. 503, d, d, arise by a thin fascia from near the lower part of the symphysis pubis, soon become fleshy, and increase in thickness as they pass outward: each muscle then returns upon itself, at an acute bend, to grasp the crus penis, and terminates in a strong tendinous expansion at the junction of the cavernous with the bulbous structures. The retractor penis,' figs. 503, 504, g, g, arises in the Kangaroo from the middle of the sacrum, and divides into two muscles,

504

Male organs, Opossum. CCXXXV".

behind the rectum, opposite the dilated commencement of the musculo-prostatic part of the urethra; each division diverges to the side of the rectum, then passes to the interspace between the rectum and roots of the penis, converging along the lateral and posterior part of the penis, to be inserted with the opposite muscle at the base of the glans. In the Opossum and those Marsupials which, having a bifid glans, enjoy, as it were, a double coitus, there is a 'levator penis,' fig. 504, ƒ, ƒ, which is not present in the

Kangaroo. Each portion of this muscle takes its origin from the fascia covering the crus penis, converges towards its fellow above the dorsum penis, diminishing as it converges, and terminates in a common tendon inserted into the upper part of the base of the glans. There is another powerful muscle which, though not immediately attached to the penis, must exert in all Marsupials an important influence upon its erection. This is the external 'sphincter cloacæ: it is an inch and a half in breadth in the Kangaroo, and half an inch in thickness; from the back of the termination of the rectum it passes over the anal glands and sides

of the base of the penis, inclosing the two bulbs with Cowper's glands and their muscles, and terminates anteriorly in a strong fascia above the dorsum penis, so as to compress against that part the venæ dorsales. In all Marsupials the penis is bent upon itself when passive and retracted; with the glans concealed just within the cloacal aperture, from which it emerges, as in oviparous Vertebrates, when the penis is turgid and erect.

§ 371. In Rodentia.-Here, likewise, the penis is habitually retracted out of view, being strongly bent, in many (e. g. Sciurus, Castor) in a sigmoid curve, with the glans directed backward, fig. 497, s, within a prepuce, which opens into, or forms part of, the common passage, ib. g, e, a, in which the rectum, ib. b, terminates. The testes undergo a periodical increase of size and change of position, passing from the abdomen into a sessile scrotum, and being again retracted, after the rut (except, perhaps, in Leporida) within the abdomen. Besides Cowperian there are prostatic and vesi

cular glands, usually large: but, again, the Leporida show their exceptional character in the Order by the absence of the latter. In the Hare (Lepus timidus) the testes make a more conspicuous prominence than in other Rodents, in their scrotal bags, one on each side the cloacal vent, fig. 505, a. The tunica vaginalis retains an opening wide enough for the repassage of the testis into the abdomen, but it adheres to the bottom of the sac, the serous membrane of which is there reflected by a fold upon the epididymis, fig. 505, h, i, and be

505

ginning of the vas deferens, ib. p, q. The testes, f, g, in this figure, have been dissected from the scrotum and tunica vaginalis. The epididymis is extended beyond the testis, as at h, i, before being reduced and reflected as vas deferens: the sperm-ducts enlarge at their termination between the urinary, e, and protometral, d, bladders, into the latter of which they open, very near

its communication with the urethra. The protometra,' d, has thin walls, except at its terminal neck, where it seems thickened by the adhesion of prostatic follicles, opening by distinct ducts into the urethra. The Cowperian glands lie at the sides of the muscular tract of the urethra, and open into it. The penis is short, consisting chiefly of a pyramidal pointed glans; it is exposed at b, in its prepuce, which opens into the subanal fossa, a, into which the preputial or ano-preputial glands, k, l, exude their firm sebaceous secretion. The erectores penis' arise from both pubis and ischium, and are inserted chiefly into the outer side of the crura corporis cavernosi: the 'levator penis' arises from the symphysis pubis, and is inserted into the glans by a small tendon, passing along the dorsum penis, over the convex bend, which it straightens when the penis is extended in erection. The Rabbit differs from the Hare chiefly in the larger relative size of the protometral vesicle, which also more commonly shows a bilobation of the base: its terminal orifice, in the urethra, is transverse and crescentic as if bent round the swellings of the verumontanum.'* Lagomys resembles Lepus in its male generative organs.

The vesicular glands are present, but small, in the Sciurine family. In the grey Squirrel they are slender, somewhat elongated bodies, bent upon the base of the prostate, through the substance of which their comparatively long ducts pass, together with the vasa deferentia. The prostate is a relatively large elongated compact body, loosely attached to the posterior part of the neck of the bladder and muscular part of the urethra. Cowper's glands are also relatively of large size; they are situated at the sides of the rectum, of a rounded conical form with the base bent forward upon the apex, from which a long, thick duct, with glandular parietes, is continued into the bulb of the urethra. The diminutive size of the so-called vesiculæ seminales' is not compensated by a dilatation of the vasa deferentia, as might have been expected had their office been to serve as a reservoir for the secretion of the testes, but by the magnitude of the other glands, viz. the prostate and Cowper's, the admitted function of which is to add some accessory fluids to the semen; and the Squirrels do not differ in the mode or duration of the act of copulation from other Rodents in which the vesicular glands are largely developed.

In the Porcupine (Hystrix cristata) the tunica vaginalis testis' adheres to the scrotum and abdominal ring by so much and so lax areolar tissue that its inversion with return of the testis to

1 CCXXXVI, vol. ii. p. 167 (note). Uterus masculinus,' ccxxxvIII". passim. Corpusculum Weberianum,' 'Vesicula prostatica,' 'Sinus prostaticus,' ccxxxx". p. 1415. 2 ccxxxix". p. 1419.