The urethra traverses the prostate from be hind forwards, and is completely surrounded by it. Amussat doubted this fact, and thought that only three fourths of the canal were en circled by the prostate, and that the remain ing fourth (the anterior) was covered by a cellular or muscular medium, extending from one lobe to the other. This is undoubtedly incorrect as a general rule, for 1 have examined with the microscope that portion of the gland placed over the upper surface of the urethra, and found it identical in structure.with the remainder of the organ. The urethra in pass ing through the prostate is dilated into a con siderable sinus, and presents in front a trian gular opening if a transverse section be made. It is not exactly in the centre, being nearer the anterior than the posterior surface ; it is generally said to be about two lines distant from the former, and four from the latter, and seven from the lateral surface of the gland. It varies frequently in this respect in a marked degree. When the third lobe is small and flat it is much nearer the posterior surface than the anterior ; and this is the case where the isthmus or medium of connection beneath, is thin, a condition not very uncommon. The prostatic portion of the urethra is about fifteen lines in length, and is wider in the middle than at either extremity ; it con tains within it the veru montanum or caput gallinaginis, which runs along it, forming a conical elevation, and dividing it into two equal portions.
Over the urethral surface of the third or middle lobe of the prostate, the mucous membrane is raised up so as in some subjects to form a remarkable elevation, lying trans versely at the beginning of the urethra ; this is especially seen in old subjects : it sponds witlt the anterior extremity of the trigonum vesicce, and is known by the names of the uvula vesicce, luette vesicale, valvula pylorica of Amussat. In the healthy state of the bladder and prostate, this elevation is frequently scarcely perceptible, unless the bladder is much contracted ; but it is subject to considerable increase in size, and is gene rally involved in those cases of enlarged pros tate which are of such frequent occurrence in the old person, and where the third lobe is the seat of hypertrophy. Mercier describes this vesico-urethral valve as a semicircular fold, raised suddenly at a right angle from the posterior surface of the neck of the bladder, and composed of a tissue somewhat resem bling muscle ; and Mr. Guthrie, in his lectures delivered at the College of Surgeons in the year 1830, directed attention to it as fre quently the seat of disease totally independent of any enlargement of the third lobe of the prostate ; but to this I shall again direct attention when the morbid anatomy of the prostate is under consideration.
Intinzate Structure. prostate comes under that division of the glandular system, inappropriately termed conglomerate. Miiller places it in his fourth order of glands—"glan dukz ex cellulorunz contextu spongioso composito, mechis cellzdis in ductus excretorios hiantibus, sine lobulorum divisione composita." It is ar ranged by Cuvier under the head of supple mentary glands of the male organs of genera tion. The external covering of the gland, de rived, as already described, from the vesical fascia, having been removed, we come to it deeper layer, which closely surrounds the glandular tissue; it is most intimately con nected with it, so as to be detached with the greatest possible difficulty', and can evi dently be shown to send processes into the gland, which are probably continuous with the fibrous tissue between the follicles. On the
surface of this the lymphatics of the gland are seen to ramify : this is best shown after pre vious immersion in water. If a simple section is made, the gland presents a spongy cellular aspect, and an opaque fluid oozes out from the cut surface ; but Its intimate structure can only be made out by microscopical examin ation of' thin sections, or by injections with mercury or coloured size, or by inflation ; the outline of its follicles may, however, be seen by a minute injection of its blood vessels, which ramify in a delicate plexiform manner on their surface. It is not a gland of much complexity of structure or arrangement. Briefly, it may be said to be composed of minute terminal follicles, opening into canals or tubes, which unite together to form ducts, which open in an oblique manner on the pros tatic portion of the urethra. The orifices of the prostatic ducts are situated principally close to and around the most elevated portion of the veru montanum, in the form of a cres cent, the larger ducts on the side, and the smaller on the posterior aspect of this body If a longitudinal, vertical section is made, many of the ducts of the prostate are seen passing upwards, towards the under part of the veru montanum, in a straight direction ; the interior of some of them being slit open in the section, whilst others pass obliquely be neath the mucous membrane for some dis tance prior to their termination. They vary in number from ten to fourteen, but as many as thirty have been seen. Their diameter ranges from one-sixth to one-fourth of a line. It sometimes happens that two or more ducts unite, and open by one common orifice, large enough to admit the end of a small probe.
To unravel the structure of the gland, it is requisite to inject the ducts separately, as the follicles to which they lead have no commu nication with each other, as the representation given by Miller would lead one to imagine ; each duct will be found to give off tubes, which passing in a straight direction, separate gradually from each other, and terminate in minute cells or follicles, which, according to Weber, range from one-sixteenth to one twelfth of a line in diameter. Miller says that the larger cells are visible to the naked eye, and that with a simple microscope the smaller cells, situated within the larger, and formed of an exceedingly delicate membrane can be seen ; the cellular structure is rendered perceptible by inflation from the ducts. Mr. John Quekett has injected with coloured size, and examined the tubes and follicles of the prostate with the microscope, and represents the latter as varying in size in different parts of the gland ; he thinks that one-hundredth of an inch is their average diameter, and has de lineated them as is shown infig. 104. Henle has found them to be lined by a delicate pave ment epithelium, and at the commencement of the duct he has seen a cylindriol epithe lium. Mr. Quekett has traced an intermediate cellular or fibrous tissue, filling up the spaces between the follicles or lobules, and connect ing them together. According to Dr. C. II. Jones, " this principally consists of the white fibrous element, but also contains numerous bands, resembling closely those of organic muscle." The latter anatomist thinks that the enlargement of the gland in hypertrophy of the prostate, is due to an increase in this tissue: he regards the prostate as an assem blage of secerning follicles rather than as a really conglomerate gland.