Part 54

The =vesiculæ seminales= are not bladder-like sacs, as in the horse, but are compact glandular organs with a lobulated surface. In the adult they measure about four or five inches (ca. 10 to 12 cm.) in length, two inches (5 cm.) in width in their largest part, and an inch or more (ca. 3 cm.) in thickness. The dorsal surface of each faces upward and inward and is partially covered with peritoneum. The ventral surface faces in the opposite direction and is non-peritoneal. Each may be regarded as consisting of a very thick-walled, sacculated tube, bent on itself in a tortuous manner. This tube, if straightened out, would be about ten inches (25 cm.) in length. They are commonly unsymmetrical in size and shape. Short branches are often given off from the chief tube. The excretory duct or neck joins the outer side of the vas deferens at an acute angle to form the ejaculatory duct.

[Illustration:

FIG. 401.—ANTERIOR EXTREMITY OF PENIS OF BULL, LEFT VIEW. (After Böhm.) ]

[Illustration:

FIG. 402.—CROSS-SECTION OF PELVIC URETHRA OF BULL.

_1_, Prostate gland (pars disseminata); _2_, urethra; _3_, urethral muscle; _4_, aponeurosis. The lumen of the urethra is black. ]

The structure of the vesicula is masked by a thick capsule of fibrous tissue and unstriped muscle, which maintains it in its bent condition and also sends trabeculæ between the alveoli. There is a central canal into which the secretion formed in the alveoli passes. The cavities (central canal and alveoli) are lined with columnar epithelium. On account of this structure the term glandulæ vesiculares is preferred by some anatomists.

The =prostate= is pale yellow in color, and consists of two parts. The =body= (Corpus prostatæ) is a mass which stretches across the dorsal surface of the neck of the bladder and the origin of the urethra. It measures about an inch and a half (ca. 3.5 to 4 cm.) transversely, and about half an inch (ca. 1 to 1.5 cm.) in width and thickness. The =pars disseminata= surrounds the pelvic part of the urethra; dorsally it forms a layer about half an inch (ca. 10 to 12 mm.) thick, but ventrally it is quite thin. It is concealed by the urethral (Wilson’s) muscle; hence it often escapes notice, but is very evident on cross-section (fig. 402). The =prostatic ducts= open into the urethra in rows between two folds of the mucous membrane which proceed backward from the colliculus seminalis.

The =uterus masculinus= appears to be absent frequently. Ellenberger states that it opens between the ejaculatory ducts, while Martin says that it usually has two orifices at the colliculus, but that it often unites with the vasa deferentia.

The =bulbo-urethral= (Cowper’s) =glands= are somewhat smaller than in the stallion. They are liable to escape notice, since they are covered by a thick layer of dense fibrous tissue and also partially by the bulbo-cavernosus muscle. Each has a single duct which opens into the urethra under cover of a fold of the mucous membrane.

The =penis= is cylindrical, and is longer and of very much smaller diameter than in the horse. Just behind the scrotum it forms an =S=-shaped curve, the =sigmoid flexure=; thus about one foot is folded up when the penis is fully retracted. The flexure is effaced during erection. The =glans penis= is about three inches (ca. 8 cm.) in length. It is flattened dorso-ventrally, and its extremity is pointed and twisted. The =external urethral orifice= is situated at the end of a groove formed by this twist; it is only large enough to admit a probe of medium size. Even in the non-erect state the penis is remarkably dense and firm. The =tunica albuginea= is very thick, and incloses the urethra. In the first part, as far as the first curve, there is a thick median =septum penis=. Beyond this there is a central axial rod of dense fibrous tissue from which numerous strong trabeculæ radiate. The erectile tissue is small in amount, so that the organ undergoes very little enlargement in erection.

The length of the penis in the adult is about three feet (ca. 90 cm.). The crura are flattened laterally. The suspensory ligaments are attached to the ventral ridge on the symphysis. The body is somewhat flattened dorso-ventrally beyond the first curve. The extremity of the glans is unsymmetrical, the urethral orifice being situated ventro-laterally. The glans contains little erectile tissue, and hence undergoes little enlargement in erection.

The =bulbo-cavernosus muscle= presents several remarkable features. It is for the greater part an inch or more (ca. 3 cm.) in thickness, but its length is only six to eight inches (15 to 20 cm.). It is covered by a strong aponeurosis, and is divided by a median raphé into two lateral halves except at its origin. It diminishes in size from behind forward, and its anterior extremity is pointed.

The =ischio-cavernosus muscle= resembles in general that of the horse, but is flattened laterally. It is covered by a close aponeurosis.

The =retractor penis= muscle resembles that of the horse in origin. Its two parts are about an inch (ca. 2 to 5 cm.) apart on the root of the penis, where they lie in a groove on either side of the bulbo-cavernosus. They then come close together and pass on either side of the ventral curve of the sigmoid flexure. Further forward they lie along the ventral aspect of the penis, and end about five or six inches (ca. 12 to 15 cm.) behind the glans.

The =prepuce= is very long and narrow. Its orifice is about two inches (ca. 5 cm.) behind the umbilicus; it is only large enough to admit a finger readily, and is surrounded by long hairs. The cavity of the sheath is about fifteen inches (35 to 40 cm.) long, and a little over an inch (ca. 3 cm.) in diameter. The lining membrane forms longitudinal folds; it is covered with squamous stratified epithelium, and has coiled tubular glands. The penile layer is glandless, and is reddish in color. It presents lymph nodules in its posterior part.

There are two pairs of =preputial muscles= which are derivatives of the panniculus carnosus. The anterior pair, the =protractors= of the prepuce (Mm. præputiales craniales), are two flat bands, two inches or more (5 to 6 cm.) in width, which arise close together in the xiphoid region, about eight inches (20 cm.) in front of the preputial orifice. Traced backward they diverge, leaving the umbilicus and an area about one and a half inches wide free, and then unite behind the preputial orifice. They draw the prepuce forward. The posterior pair, the =retractors= of the prepuce (Mm. præputiales caudales), arise in the inguinal region and converge on the anterior part of the prepuce. They draw the prepuce backward.

These muscles are subject to a good deal of variation. The retractor may be absent. Many fibers come in from the panniculus on either side, dip under the protractor, and are inserted into the skin just behind the preputial opening. The homologue of the protractor is present in the cow.

The =urethra= in its pelvic part is about five inches (12 cm.) long, and is of relatively small and uniform caliber. The =urethral= (Wilson’s) =muscle= incloses the tube ventrally and laterally; it is very thick, crescentic in cross-section, and is covered by an aponeurosis. Dorsally, the aponeurosis is thick and the muscle absent. Inside of these the pars disseminata of the prostate surrounds the urethra as far back as the bulbo-urethral glands. The =colliculus seminalis= is short, but prominent; from it the urethral crest extends forward to the trigonum vesicæ. The extrapelvic part has an enlargement, the =bulb=, at its origin; it then gradually diminishes in diameter, and is relatively very small at its termination. Other features have been mentioned in preceding paragraphs.

[Illustration:

FIG. 403.—ANTERIOR PART OF PENIS OF RAM.

_A_, Right side; _B_, left side. (After Böhm.) ]

In the ram the urethra lies in a groove on the ventral surface of the corpus cavernosum. Its terminal part projects commonly 3 to 4 cm. beyond the glans penis, forming a twisted processus urethræ.

MALE GENITAL ORGANS OF THE PIG

The =scrotum= is situated a short distance from the anus, and is not so sharply defined from the surrounding parts as in the other animals.

The =testicles= are very large and are soft in texture. Their long axis is almost vertical, the free border being posterior and the tail of the epididymis dorsal. The mediastinum testis is well developed. The epididymis is closely attached to the testicle and the tunica vaginalis; the tail is specially large.

The =spermatic cord= is necessarily very long (20 to 25 cm. in a boar of medium size). The =vas deferens= in its testicular part is flexuous, and is closely attached to the tunica vaginalis; it forms no ampullæ. The =cremaster externus= is well developed, and extends to about the middle of the scrotal part of the tunic.

The =vesiculæ seminales= are exceedingly large, and extend into the abdominal cavity. They are three-sided pyramidal masses, are in apposition with each other medially, and cover the posterior part of the bladder and the ureters, the vasa deferentia, the body of the prostate, and the anterior part of the urethra. They are pale pink in color, distinctly lobulated and glandular in structure, and contain large alveoli, but no central cavity. There are two excretory ducts which open into the urethra close to the vasa deferentia; the two ducts frequently unite.

In the adult boar the vesiculæ are about five to six inches (ca. 12 to 15 cm.) long, two to three inches (ca. 5 to 8 cm.) wide, and one and a half to two inches (ca. 4 to 5 cm.) thick; they weigh about 6 to 8 ounces each.

The =prostate= consists of two parts, as in the ox. The =body= is about an inch (2.5 cm.) wide, and embraces the neck of the bladder and the urethra at their junction dorsally and laterally. It is concealed by the vesiculæ seminales. The =pars disseminata= forms a layer which surrounds the pelvic part of the urethra, and is covered by the urethral muscle.

The uterus masculinus is small.

The =bulbo-urethral= (Cowper’s) =glands= are very large and dense. They are somewhat cylindrical, and lie on either side of and upon the posterior two-thirds of the pelvic urethra. In a large boar they are about five inches (ca. 12 cm.) in length and an inch or more (ca. 2.5 to 3 cm.) in diameter. They are partially covered with a layer of striated muscle (M. ischio-glandularis), and have a lobulated surface. Each gland has a large excretory duct which leaves at the posterior extremity, perforates the dorsal wall of the urethra at the ischial arch, and opens in a cul-de-sac covered by a fold of mucous membrane.

[Illustration:

FIG. 404.—GENITAL ORGANS OF BOAR.

_a_, Testicle; _b_, epididymis; _c_, vas deferens; _d_, spermatic artery; _e_, vesicula seminalis reflected to show the body of the prostate, _f_; _e′_, excretory ducts of vesiculæ; _g_, bulbo-urethral (Cowper’s) gland; _h_, urinary bladder; _i_, urethral muscle; _k_, bulbo-cavernosus muscle; _l_, penis; _l′_, sigmoid flexure of penis; _l″_, spiral anterior part of penis, exposed by slitting open prepuce; _m_, orifice of preputial pouch; _n_, retractor penis muscle. (Ellenberger-Baum, Anat. d. Haustiere.) ]

It is to be noted that these accessory glands are very small in animals which have been castrated early.

The =penis= resembles in general that of the ox. The sigmoid flexure is, however, prescrotal. The anterior portion has no glans, and is spirally twisted, especially in erection. The =urethral orifice= is slit-like and is situated ventro-laterally, close to the pointed extremity. The penis in the adult boar measures about 18 to 20 inches (ca. 45 to 50 cm.) in length. Its muscles resemble those of the bull; the bulbo-cavernosus is very strong but short.

The =prepuce= has a narrow orifice, around which there are a number of stiff hairs. The cavity is partially divided by a circular fold into a posterior narrow portion and a much wider anterior portion. The lining membrane of the posterior part is papillated, and is in close contact with the penis. In the dorsal wall of the wide part there is a circular opening which leads into a cul-de-sac, the =preputial diverticulum=. This pouch is ovoid in form (when distended), and varies greatly in size in different subjects. It extends for the most part backward over the narrow part of the prepuce. Its cavity is partially divided by a narrow median septum. It contains usually decomposing urine and macerated epithelium, which have a characteristic and very unpleasant odor. Concrements have been found in it.

Oehmke found that a cast of the pouch in a Yorkshire boar weighing about 500 pounds measured 9 cm. in length, 12½ cm. in breadth, and 6 cm. in height. The opening into the prepuce will admit two fingers in the adult, but is ordinarily closed by folds of the lining membrane. The sac is much smaller in animals which were castrated young, and the opening is vertical and further back; in them it is often empty or contains only a little clear urine. The pouch is covered by a layer of striped muscle which is mainly derived from the homologue of the protractor of the prepuce of ruminants.

The =urethra= has a very long pelvic portion (ca. 15 to 18 cm. long in the adult); it is inclosed (with the pars disseminata of the prostate) by a thick =urethral muscle=. There is a distinct =bulb= at the root of the penis. The penile part is of small caliber, and is surrounded by erectile tissue which, however, does not extend to the extremity of the penis.

MALE GENITAL ORGANS OF THE DOG

The =scrotum= is situated about half-way between the inguinal region and the anus. The skin covering it is pigmented and is covered sparsely with fine hairs. The raphé is not very distinct.

The =testicles= are relatively small, and have a round-oval form. The long axis is oblique, and is directed upward and backward. The mediastinum testis is central and is well developed. The epididymis is large, and is closely attached along the outer part of the dorsal border of the testicle.

The =spermatic cord= and the =tunica vaginalis= are long; they cross the side of the penis very obliquely. The upper end of the tunic is sometimes closed, so that there is then no vaginal ring. The vasa deferentia have very narrow ampullæ.

The =vesiculæ seminales= are absent; hence there are no ejaculatory ducts.

The =prostate= is relatively large; it is yellowish in color, dense in structure, and lies at the anterior border of the pubis. It is globular, and surrounds the neck of the bladder and the urethra at their junction. A faint median furrow indicates a division into two lateral lobes. The capsule and stroma contain a large amount of unstriped muscle. The ducts are numerous. Lobules of prostatic tissue (pars disseminata) are also found on the urethra further back. The gland is subject to much variation in size, and is often enlarged, especially in old subjects.

The =uterus masculinus= is a very small saccule (Utriculus prostaticus), often difficult to find.

The =bulbo-urethral= (Cowper’s) =glands= are absent.

The =penis= presents several special features. In its posterior part there are two distinct corpora cavernosa, separated by a median septum penis. In its anterior part there is a bone, the =os penis=, which in large dogs reaches a length of four inches (ca. 10 cm.) or more. It is regarded as a continuation forward of the corpus cavernosum. Ventrally it is grooved for the urethra; dorsally it is convex, and anteriorly it becomes smaller and has a curved fibrous prolongation. The =glans penis= is very long, extending over the entire length of the os penis; posteriorly it forms a rounded enlargement, the =bulbus glandis=; anteriorly it is cylindrical, smaller, and pointed at the extremity. Just in front of the bulbus glandis there is a thick circular layer of glands, forming the =annulus glandularis= (Schmaltz). The two dorsal veins arise from the bulbus glandis, pass backward on the dorsum penis, and unite at the ischial arch. A small muscle (M. compressor venæ dorsalis penis) arises from the tuber ischii on either side; the two converge on the dorsum penis near the bulbus glandis. They compress the dorsal veins, and may also tend to elevate the penis and thus assist in copulation. The other muscles offer no features worthy of special description.

The =prepuce= forms a complete sheath around the anterior part of the penis. The outer layer is ordinary integument. The inner layer has the character of a glandular mucous membrane; it is thin and reddish in color. The penile layer is glandless. In the fundus of the præputial cavity there are numerous lymph follicles. The protractor muscles arise in the xiphoid region and decussate posteriorly around the extremity of the penis.

[Illustration:

FIG. 405.—EXTERNAL GENITAL ORGANS OF MALE DOG, VENTRO-LATERAL VIEW OF PREPARATION.

_1_, Scrotum; _1′_, tunica vaginalis; _2_, epididymis; _3_, vascular part of spermatic cord; _4_, vas deferens; _5_, prepuce; _6_, glans penis; _6′_, corpus cavernosum penis; _7_, bulbus glandis; _7′_, contour of bulbus in erection; _8_, ischio-cavernosus muscle; _a_, acetabulum; _b_, obturator foramen. (After Ellenberger, in Leisering’s Atlas.) ]

[Illustration:

FIG. 406.—INTERNAL GENITAL ORGANS OF MALE DOG.

_1_, Urinary bladder; _2_, ureter; _3_, vas deferens; _4_, prostate; _5_, urethral muscle; _6_, bulb of urethra; _a_, abdominal wall; _b_, ilium; _c_, ischium. (After Ellenberger, in Leisering’s Atlas.) ]

The pelvic part of the =urethra= is relatively long. Its first part is inclosed in the prostate.[148] At the ischial arch the urethra has a well-developed bilobed =bulb=, formed by an enlargement here of the corpus spongiosum. It is covered by the strong but short bulbo-cavernosus muscle. The other erectile bodies have been described.

The =urethral= (Wilson’s) =muscle= is very strong; it encircles the urethra and has a median raphé dorsally.

THE FEMALE GENITAL ORGANS

The =female genital organs= (Organa genitalia feminina) are: (1) The two =ovaries=, the essential reproductive glands, in which the ova are produced; (2) the =uterine= or =Fallopian tubes=, which convey the ova to the uterus; (3) the =uterus=, in which the ovum develops; (4) the =vagina=, a dilatable passage through which the fœtus is expelled from the uterus; (5) the =vulva=, the terminal segment of the genital tract, which serves also for the expulsion of the urine; (6) the =mammary glands=, which are glands of the skin, but are so closely associated functionally with the generative organs proper as to be described with them.

GENITAL ORGANS OF THE MARE

THE OVARIES

[Illustration:

FIG. 407.—LATERAL VIEW OF GENITAL ORGANS AND ADJACENT STRUCTURES OF MARE.

The removal of the other abdominal viscera has allowed the ovaries and uterus to sink down, whereas they are normally in contact with the roof of the cavity in the non-pregnant subject. _1_, Left ovary; _2_, Fallopian tube; _3_, left cornu uteri; _4_, right cornu uteri; _5_, corpus uteri; _5′_, portio vaginalis uteri, and _5″_, os uteri, seen through window cut in vagina; _6_, broad ligament of uterus; _6″_, round ligament; _7_, vagina; _8_, labia vulvæ; _9_, rima vulvæ; _9′_ superior commissure, and _9′_, inferior commissure of vulva; _10_, constrictor vulvæ; _11_, position of vestibular bulb; _12_, ventral wall of abdomen; _13_, left kidney; _14_, left ureter; _15_, urinary bladder; _16_, urethra; _17_, rectum; _18_, anus; _19_, _19′_, unpaired and paired parts of sphincter ani externus; _20_, retractor ani cut at disappearance under sphincter; _21_, suspensory ligament of anus; _22_, longitudinal muscular layer of rectum; _22′_, recto-coccygeus; _23_, constrictor vaginæ; _a_, utero-ovarian artery, with ovarian (_a′_) and uterine (_a″_) branches; _b_, uterine artery; _c_, umbilical artery; _d_, ischium; _e_, pubis; _f_, ilium. (After Ellenberger, in Leisering’s Atlas.) ]

The =ovaries= (Ovaria) of the mare are bean-shaped, and are much smaller than the testicles. Their size varies much in different subjects, and they are normally larger in young than in old animals; one ovary is often larger than the other. They are about three inches (ca. 7 to 8 cm.) long and an inch to an inch and a half (ca. 3 to 4 cm.) thick. The weight is about two and a half to three ounces (ca. 70 to 80 grams).

Each presents for description two surfaces, two borders, and two extremities or poles. The =surfaces= are termed internal and external (Facies medialis, lateralis); they are both smooth and rounded.[149] The =attached= or =mesovarial border= (Margo mesovaricus) is convex. It is inclosed in a part of the broad ligament termed the mesovarium; the vessels and nerves reach the gland at this border. The =free border= (Margo liber) is marked by a notch which leads into a depression, the =ovulation fossa=. The =tubal= or =anterior extremity= (Extremitas tubaria) is rounded, and is related to the fimbriated end of the uterine or Fallopian tube. The =uterine= or =posterior extremity= (Extremitas uterina) is also round, and is connected with the horn of the uterus by the ovarian ligament.

The ovaries are situated in the sublumbar region of the abdominal cavity, about a handbreadth behind the corresponding kidney. They are in contact with the lumbar wall of the abdomen, and are commonly about two or three inches (ca. 5 to 7.5 cm.) from the median plane. The distance from the ovaries to the vulvar orifice is about twenty inches (ca. 50 cm.) in a mare of medium size. The attached (mesovarial) border is commonly directed toward the median plane, the free border laterally and somewhat ventrally.

The position of the ovaries is not constant, but is subject to less variation than might be expected from their mode of attachment. The normal variations in the non-pregnant state are chiefly in a transverse direction, and do not usually exceed two or three inches (ca. 5 to 7 cm.). It is not at all rare to find the ovary deflected medially, so that the external surface faces ventrally. In the longitudinal direction little variation appears to occur. The right ovary is usually about four or five inches (ca. 10 to 12 cm.), and the left one about three or four inches (ca. 8 to 10 cm.), behind the corresponding kidney. Thus they lie about in a transverse plane tangent to the external angles of the ilia, i. e., through the fifth lumbar vertebra. They may be about two inches (ca. 5 cm.) from the extremity of the corresponding cornu of the uterus or in contact with it. The right ovary commonly lies a little (ca. 2.5 cm.) further forward than the left one. Except during pregnancy, they are normally in contact with the lumbar abdominal wall, and do not hang down among the adjacent viscera.

[Illustration:

FIG. 408.—RIGHT OVARY OF MARE, WITH ADJACENT STRUCTURES.

The extremity of the cornu uteri is opened. _1_, Ovary; _2_, Fallopian tube, with its ostium abdominale (_2′_), fimbriæ (_2″_), and ostium uterinum (_2‴_); _3_, cornu uteri, with its mucous lining (_3′_); _4_, ovarian ligament; _4′_, mesosalpinx. (After Ellenberger, in Leisering’s Atlas, reduced.) ]

The ovary is attached to the sublumbar region by the anterior part of the broad ligament; this part of the ligament, the =mesovarium=, is about three or four inches (ca. 8 to 10 cm.) wide, measured from the ovary directly to the parietal attachment. The uterine or posterior extremity of the ovary, is connected with the extremity of the cornu of the uterus by the =ovarian ligament= (Ligamentum ovarii proprium); this is a band of unstriped muscle inclosed between the layers of the broad ligament.