File:The chordates (1950) (20423739228).jpg

Title: The chordates
Identifier: chordates00rand (find matches)
Year: 1950 (1950s)
Authors: Rand, Herbert W. (Herbert Wilbur), 1872-1960
Subjects: Chordata
Publisher: Philadelphia : Blakiston
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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Mammalia: Visceral Systems 663
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Fig. 500. Diagram of male genitalia of beaver, Casior canadensis. Penis re- tracted into the floor of the shallow cloaca, (a) Anns; (ag) anal gland; (6) urinary bladder; (gv) gland of vas deferens; (oa) opening of anal gland; (op) os penis; (p) prostate; (pp) preputial gland; (r) rectum; (u) urethra; (vd) vas deferens. (After Weber. Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Philadelphia, The Blakiston Company.) penis is directed downward or more or less forward (Fig. 496). In those insectivores and rodents which have more or less of an ectodermal cloaca as in marsupials, the retracted penis is drawn into the cloaca, pointing backward. The right and left scrotal sacs lie laterally in the perineal region but are so shallow as to cause little external protrusion. Accessory Genital and Anal Glands At certain regions in the more posterior part of the male urino- genital tract, the walls of the passages are glandular or may give rise to appended glandular organs. Their common function seems to be secretion of a mucous fluid which serves as a carrier for the sperma- tozoa and provides a medium favorable for their survival and activity. In some cases (rodents) the secretion coagulates in the vagina, thus favoring fertilization by preventing escape of the spermatic fluid. These glands are distinguished mainly by their position in relation to the passages (Fig. 492). In the more posterior region of each vas deferens, but anterior to its ejaculatory region, the wall may be thick and glandular or, more commonly, it gives rise to a pair of large and more or less complexly subdivided glands, often called "seminal vesicles," but better known as vesicular glands because they are essentially secretory rather than for mere storage of sperm. Especially important glands occur along the neck of the bladder and the urethra. The prostate is usually a massive gland divided into a varying number of lobes, situated just posterior to the junction of the vasa deferentia w itli the neck of the bladder. At the base of the prostate, or embedded in the gland, is commonly found a small and usually bilobed vesicle protruding from the wall of the urethra. This prostatic vesicle or utriculus is a remnant of the embryonic Miillerian ducts. It is usually known as the "uterus masculinus," but, being derived from the

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