renal artery, and terminates in an efferent vessel. Several of these latter form, by their anastomosing ramifications, the plexus that surrounds each urinary conduit and tubule; the urinary conduits being lined by thick epithelium, and their necks furnished with vibratile cilia. All the blood of the renal artery, according to Mr. Bowman,with the exception of a small quantity distributed to the capsule, surrounding fat, and the coats of the larger vessels,-enters the capillary tufts of the corpora Malpighiana; thence passes into the capillary plexus surrounding the uriniferous tubes, and finally leaves the organ through the branches of the renal vein. According to this view, there are in the kidney two perfectly distinct systems of capillary vessels; the first, that inserted into the dilated extremities of the uriniferous tubes, and in immediate connexion with the arteries-the Malpighian bodies: the second, that enveloping the convolutions of the tubes, and communicating directly with the veins. The efferent vessels of the Malpighian bodies, that carry the blood between these two systems, are termed by Mr. Bowman the portal system of the kidney. The views of Mr. Bowman have been embraced by many histologists, whilst every one of them has been strenuously denied by others. In regard to the precise arrangement of the Malpighian bodies, histologists are by no means in accordance. Gerlach for example, found, that instead of the flask-like dilatation being placed, as maintained by Mr. Bowman, at the extremity of a uriniferous tube, it may be, and is formed by off-sets from the sides of the tube; so that the capsules may be either terminal or lateral.3

2

In the quadruped, each kidney is made up of numerous lobes, which are more or less intimately united according to the species. In birds, the kidney consists of a double row of distinct, but connected, glandular bodies, placed on both sides the lumbar vertebræ.

The ureter is a membranous duct, which extends from the kidney to the bladder. It is about the size of a goosequill; descends through the lumbar region; dips into the pelvis by crossing in front of the primitive iliac vessels and the internal iliac; crosses the vas deferens at the back of the bladder; and, penetrating that viscus obliquely, terminates by an orifice ten or twelve lines behind that of the neck of the bladder. At first, it penetrates two of the coats only of that viscus; running for the space of an inch between the mucous and muscular, and then entering the cavity. The ureters have two coats. The outermost is a dense fibrous membrane; the innermost a thin mucous layer, continuous at its lower extremity with the inner coat of the bladder; and, at the upper end, supposed by some to be reflected over the papillæ, and even to pass for some distance into the tubuli uriniferi.

The bladder is a musculo-membranous sac, situate in the pelvis; anterior to the rectum, and behind the pubes. Its superior end is called

1 See Fig. 48, vol. i. p. 132.

2 See on the whole subject Dr. Geo. Johnson, in the article Ren, Cyclopædia of Anatomy and Physiology, Pt. xxxii. p. 244, Lond., August, 1848; and Gerlach, Handbuch der Gewebelehre, s. 301, Mainz, 1849; and A. H. Hassall, The Microscopic Anatomy of the Human Body, Pt. xiii. p. 427, Lond., 1848.

3 Gerlach, op. cit., and in Müller's Archiv. für Anatomie, s. 378, 1845; and Ibid., s. 102,

upper fundus; and the lower end, inferior fundus or bas-fond; the body being between the two. The part where it joins the urethra is the neck. The shape and situation of the organ are influenced by age and sex. In very young infants, it is cylindroid, and rises almost wholly into the abdomen. In the adult female, who has borne many children, it is nearly spherical; has its greatest diameter transverse, and is more capacious than in the male. Like the other hollow viscera, the bladder consists of several coats. 1. The peritoneal, which covers only the fundus and back part. Towards the lower portion the organ is invested by areolar membrane, which takes the place of the peritoneal coat of the fundus. This tissue is very loose, and permits the distension and contraction of the bladder. 2. The muscular coat is very strong; so much so, that it has been classed amongst the distinct muscles, under the name detrusor urinæ. The fibres are pale, unstriped, and pass in

Lateral View of the Viscera of the Male Pelvis. (Quain.)

a. Bladder. b. b'. Rectum. c. Membranous portion of the urethra. d. Section of left crus, or corpus cavernosum. e. Bulbous extremity of corpus spongiosum or bulb of urethra. f. Cowper's gland. g. Section of body of pubes. h. Sphincter ani muscle. i. Part of left vas deferens. m. Articular surface of sacrum. n. Spine of left ischium sawn off. o. Coccyx. p. Prostate gland. r, r. Peritoneum. r. Cul-de-sac between bladder and rectum. u. Left ureter. v. Left vesicula seminalis.

various directions. Towards the lower part of the bladder, they are particularly strong; arranged in fasciculi, and form a kind of network of muscles enclosing the bladder. In cases of stricture of the urethra, where much effort is necessary to expel the urine, these fasciculi acquire considerable thickness and strength. 3. The mucous or villous coat is the lining membrane, which is continuous with that of the ureters and urethra, and is generally rugous in consequence of its being more extensive than the muscular coat without. It is furnished with numerous follicles, which secrete a fluid to lubricate it. Towards the neck of the

organ, it is thin and white, although reddish in the rest of its extent. A fourth coat, called the cellular, has been reckoned by most anatomists, but it is nothing more than areolar tissue uniting the mucous and muscular coats. The part of the internal surface of the bladder, situate immediately behind and below its neck, and occupying the space between it and the orifices of the ureters, is called vesicle triangle, trigonus Lieutaudi or trigone vésical. The anterior angle of the triangle looks into the orifice of the urethra, and is generally so prominent, that it has obtained the name uvula vesicæ. It is merely a projection of the mucous membrane, dependent upon the subjacent third lobe of the prostate gland, which, in old people, is frequently enlarged, and occasions difficulty in passing the catheter. The neck of the bladder penetrates the prostate; but, at its commencement, it is surrounded by loose areolar tissue, containing a very large and abundant plexus of veins. The internal layer of muscular fibres is here transverse; and they cross and intermix with each other in different directions, forming a close, compact tissue, which has the effect of a particular apparatus for retaining the urine, and has been called the sphincter. Anatomists have not usually esteemed this structure to be distinct from the muscular coat at large; but Sir Charles Bell' asserts, that if we begin the dissection by taking off the inner membrane of the bladder from around the orifice of the urethra, a set of fibres will be discovered on the lower half of the orifice, which, being carefully dissected, will be found to run in a semicircular form around the urethra. These fibres make a band of about half an inch in breadth, particularly strong on the lower part of the opening; and having ascended a little above the orifice on each side, they dispose of a portion of their fibres in the substance of the bladder. A smaller and somewhat weaker set of fibres will be seen to complete their course, surrounding the orifice on the upper part. The arteries of the bladder proceed from various sources, but chiefly from the umbilical and common pudic. The veins return the blood into the internal iliacs. They form a plexus of considerable size upon each side of the bladder, particularly about its neck. The lymphatics accompany the principal veins of the bladder, and, at the under part and sides, pass into the iliac glands. The nerves are from the great sympathetic and sacral.

The urethra is the excretory duct of the bladder. It extends, in the male, from the neck of the bladder to the extremity of the glans; and is from seven to ten inches in length. In the female it is much shorter. The male urethra, in the state of flaccidity of the penis, has several curvatures; but is straight, or nearly so, if the penis be drawn forwards and upwards, and the rectum be empty. The first portion of this canal, which traverses the prostate gland, is called the prostatic portion. Into it open,―on each side of a caruncle, called verumontanum, caput gallinaginis or crista urethralis,-the two ejaculatory ducts, those of the prostate, and a little lower, the orifice of Cowper's glands. Between the prostate and the bulb is the membranous part of the urethra, which is eight or ten lines long. The remainder of the canal is called corpus

I 1 Anatomy and Physiol., 5th Amer. edit. by Dr. Godman, ii. 375, New York, 1829.

spongiosum or spongy portion, because surrounded by an erectile spongy tissue. It is situate beneath the corpora cavernosa, and passes forward to terminate in the glans, the structure of which will be considered under Generation. At the commencement of this portion of the urethra is the bulb, the structure of which resembles that of the corpora cavernosa of the penis-to be described hereafter. The dimensions of the canal are various. At the neck of the bladder it is considerable: behind the caput gallinaginis it contracts, and immediately enlarges in the forepart of the prostate. The membranous portion is narrower; and in the bulb the channel enlarges. In the body of the penis, it diminishes successively, till near the glans, when it is so much increased in size as to have acquired the name fossa navicularis. At the apex of the glans it terminates by a short vertical slit. Mr. Shaw' has described a set of vessels, immediately on the outside of the internal membrane of the urethra, which, when empty, are very similar in appearance to muscular fibres. These vessels, he remarks, form an internal spongy body, which passes down to the membranous part of the urethra, and forms even a small bulb there. Dr. Horner, however, says, that this appeared to him to be rather the cellular membrane connecting the canal of the urethra with the corpus spongiosum. The whole of the urethra is lined by a very vascular and sensible mucous membrane, which is continuous with the inner coat of the bladder. It has, apparently, a certain degree of contractility; and therefore, by some anatomists, is conceived to possess muscular fibres. Sir Everard Home, from the results of his microscopical observations, is disposed to be of this opinion. This is, however, so contrary to analogy, that it is probable the fibres may be seated in the tissue surrounding it. The membrane contains numerous follicles, and several lacunæ, one or two of which, near the extremity of the penis, are so large as occasionally to obstruct the catheter, and convey the impression that a stricture exists.

The prostate and glands of Cowper, being more concerned in generation, will be described hereafter.

There are certain muscles of the perineum, that are engaged in the expulsion of the urine from the urethra; and some of them in defecation, and the evacuation of sperm likewise; - as the acceleratores urinæ or bulbo-urethrales, which propel the urine or semen forward; the transversus perinei or ischio-perinealis, which dilates the bulb for the reception of the urine or sperm; the sphincter ani, which draws down the bulb, and aids in their ejection; and the levator ani, which surrounds the extremity of the rectum, the neck of the bladder, the membranous portion of the urethra, the prostate gland, and a part of the vesiculæ seminales, and assists in the evacuation of the bladder, vesiculæ seminales, and prostate. A part of the levator, which arises from the pubis and assists in inclosing the prostate, is called by Sömmering compressor prostata. Between the membranous part of the urethra, and that portion of the levator

1 Manual of Anatomy, ii. 118, Lond., 1822.

2 Lessons in Practical Anatomy, 3d edit., p. 272, Philad., 1836.

3 For Dr. Horner's views on the origin of the acceleratores urinæ, see his Special Anatomy and Histology, 7th edit., Philad., 1848.

Fig. 357.

Part of the Ossa Pubis and Ischia, with the

ani, which arises from the inner side of the symphysis pubis, a reddish, areolar, and very vascular substance exists, which closely surrounds the canal, has been described by Mr. Wilson' under the name compressor urethra, and is termed, by some of the French anatomists, muscle de Wilson. By many, however, it is considered to be a part of the levator ani. M. Amussat asserts, that the membranous part of the urethra is formed externally of muscular fibres, which are susceptible of energetic contraction; and M. Magendie confirms his assertion.

With regard to the urinary organs of the female:-the kidneys and ureters have the same situation and structure as those of the male. The bladder, also, holds Root of the Penis attached. (Kobelt.) the same place behind the pubis; a, a. Accelerator urinæ muscle, embracing the but rises higher when distended. the middle line, e, behind. b, b. Anterior slips of It is proportionally larger than the accelerator muscle, which pass round to the dorsum of the penis. c, c. Crura of the penis. d, d. that of the male, and is broader Erectores penis muscles lying on the crura. f. The from side to side, thus permitcorpus spongiosum urethræ. g, to g. Enlargement of the crus, named the bulb of the corpus caverno- ting the greater retention to which females are often necessitated. The urethra is much shorter, being only about an inch and a half or two inches long; and it is straighter than in the male, having only a slight curve downwards between its extremities, and passing almost horizontally under the symphysis pubis. It has no prostate gland, but is furnished, as in the male, with follicles and lacunæ, which provide a mucus to lubricate it.

sum.

In birds, in general, and in many reptiles and fishes, the urine, prior to expulsion, is mixed with the excrement in the cloaca. Nothing analogous to the urinary organs has been detected in the lowest classes of animals, although in the dung of the caterpillars of certain insects, traces of urea have been met with.

The urine is formed from the blood in the kidneys; and it has, until recently, been the universal belief, that it is secreted from arterial blood; Mr. Bowman, however, in accordance with views on the minute anatomy of the kidney already given, has attempted to show, that it is separated from venous blood. His main conclusions are as follows:-First. The epithelium lining the tubes is the proper organ that secretes the characteristic products of urine from the blood; and

1 Lectures on the Structure and Physiology of the Urinary and Genital Organs, Lond., 1821. 2 Précis, &c., ii. 472.