Title: The cyclopædia of anatomy and physiology
Identifier: cyclopdiaofana03todd (find matches)
Year: 1847 (1840s)
Authors: Todd, Robert Bentley, 1809-1860
Subjects: Anatomy; Physiology; Zoology
Publisher: London, Sherwood, Gilbert, and Piper
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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392 MONOTREMATA. Fig. 190.
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Male organs, Ornithorhynchus. (Meckel.) The Monotremes are true testlconda, and in this respect differ from the Marsupial animals. In the Echidna each testicle is situated imme- diately below, or sacrad of, the kidney, and is suspended to that gland by a fold of peritoneum; the same fold is continued to the neck of the bladder, inclosing the vas deferens, which is disposed in a series of close transverse folds throughout its whole course. It corresponds closely, in these respects, with the Ornitho- rhynchus. In neither Monotreme is there any disparity of size between the right and left testicle : the latter is figured in situ at u',Jig.\Q7. The vas defer ens (fig. 190, f) emerges from the upper or atlantal extremity of the testis (e) ; and, from its peculiarly extended, plicated, or folded course, seems to prolong the epididymis nearly to the neck of the bladder; the folds gradually diminish, and the duct itself enlarges, as it approaches its termination, which is in the beginning of the urogenital canal (g). This canal is continued through the pelvis and termi- nates in the vestibular passage, anterior to the orifice of the rectum (q). The vascular tissue of the penis com- mences at the termination of the urogenital canal; it is separated by a median septum into two lateral moieties, and both are in- closed by a common dense fibrous sheath. The whole penis in its collapsed and retracted state is about fifteen lines in length, and is con- cealed in a large preputial sheath. The ter- minal half of the penis is formed by the glans, which presents a quadrilateral form, and is traversed by a median longitudinal furrow upon both the upper and the under surface. Its ex- terior is beset with numerous short and hard epidermal spines : its extremity is bifurcated, and each lobe is directed outwards and termi- nates in three or four spines, (/c, /c,) much larger, but softer, than the rest, and which are usually retracted in a depression. A longitudinal azygos levator muscle runs along the upper surface of the penis; it arises by two lateral slips from the internal stratum (w) of the protrusive sphincter. Another lon- gitudinal but longer and more slender muscle, the retractor penis, (fig- 190, p,) arises from the upper part of the base of the tail, bends downwards over the caudal muscles and vessels, and is inserted into the origin of the penis near the termination of the urogenital canal. The true urethra or canal of the penis begins by a small orifice at the root of the penis, near the termination of the urogenital passage, and by the combined action of the last described muscle with the sphincter cloacae, it can be brought into closer approximation with the uro- genital passage. It must be supposed that this temporary continuation of the urethra and urogenital passages takes place during the vigo- rous muscular and vascular actions of the parts in coitu, and that the semen is then propelled from the one along the other without escaping into the common vestibular compartment of the cloaca. Under ordinary circumstances, as when the urine is transmitted along the uro- genital passage, it must escape into the vesti- bule, and may there be blended, as in the Bird, with the rectal excrement. The true seminal urethra, commencing by the distinct aperture, as above described, is about a line in diameter, and continues single to the middle of the glans, where it divides into two canals; each branch runs along the middle of the bifurcation of the glans, and, when arrived at the base of the large papillae, subdivides into smaller channels cor- responding with the number of the papilla?, and opening upon their apices. If the canal of the penis were slit open along its under part and thus converted into a groove, the male organs of the Ornithorhynchus would be then essentially like those of a Tortoise. The adhe- sion to the Mammalian type is manifested in a highly interesting manner by the completeness of the urethral canal, whilst the affinity to the Marsupial order is evinced in its bifurcation, corresponding with that of the glans itself. Had the penis been neither perforated nor grooved, as Cuvier once believed, the structure would have been extremely anomalous. That the existence of a penis is essentially and subordi- nately related to the sexual organs and not to the renal, is beautifully illustrated by the complete separation of the uro-urethral from the semino- urethral passages in the Monotremata. The modifications by which the male organs in the Echidna differ from those of the Ornithor- hynchus, are confined to the glans penis, which divides into four mammiloid processes, rough- ened by minute papillae, and terminated by a depression in which is the branch of the semi- nal canal that traverses each process. Cowper's glands C/g.180, k, k, andjig.190, K) are of large relative size; they are situated between the base of the penis, the arch of the ischium, and internal part of the thigh : their secretion is carried by a long and slender duct (Jig. 190, »i)into the

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