Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/322

 27-2 A N• A T The tunica vaginalis is the mod confiderable of the three, and. muft be defcribed firft, in order to conceive the ftructure and connexion of the cremafter, which is very improperly called a coat. The albuginea has been already defcribed with the teftes. The tunica vaginalis is a continuation of the vagina at the fper.matic rope, .which, as it approaches the tedicle, is gradually dilated, and forms two capfulse, one contained within the other, the ext-mal being the longed and broaded at bottom; fo that there is a void fpace there left between them, in which the tedicle is lodged. The inner furface of this coat is lined by a fine membrane, which drengthens the bottom of the vagina, and forms a kind of diaphragm, which prevents all communication between the vagina of the fpermatic rope and the tunica vaginalis of the tedicle. • The cremafter, improperly termed a coat, is a thin rcufcle or fklhy -plane, which runs down round the vagina of the fpermatic rope, and terminates in the tunica vaginalis of the tefticle. It furrounds almoft the whole yagina, and afterwards expands itfelf on the upper and external part of the tunica vaginalis, in which it is inferted and loft. . It arifes partly from the ligamentum Fallopii, and partly from the lower edge 4of the internal oblique mufcle of the abdomen; and on this account it feems fometimes to arife from the fpine of the os ilium. The corpora cavernofa are two ligamentary and very limber tubes, united laterally to each fide, through the greateft part of their length, and folid at their two extremities, two of which are connected together, and rounded like the end of a finger; the other two divaricate, like the branches of the greek Y, and diminifhing gradually in fize after the divarication, termihate in an oblique point. Thefe divaricated and pointed extremities may be called the roots, and the round extremities the heads. . Thefe two bodies are almoft cylindrical, being round, and of an equal diameter from the roots to the heads, where they are in fome meafure conical. The ligamentary fubftance of their fides is eladic, and compofed of fine clofe fibres, which are partly tranfverfe, and partly more or lefs oblique. The cavity of thefe ligamentary tubes is entirely filled by a ftrong cellular or cavernous fubftance, which does not feera to be a continuation of the fubftance of the fides. Thefe cells communicate with each other, and ar.e always more or lefs full of blood, rdembling pretty much the cellular fubftance of the fpleen ; only with this difference,- that the fades of the cells are thicker in thefe cavernous bodies, and without any additional fubftance. By the union of the two corpora cavernofa, two external grooves are formed, one on the upper fide, the other on the lower. The lower groove is fomething broader than the upper, and it is filled through its whole length by a third tube, narrower than the corpora cavernofa, calledThe the urethra. roots of the corpora cavernofa are fixed, each, to the edge of ‘the fraall ramus of the os ifchium and os

O M- Y Part VI; pubis. They meet at the fymphyfis of the offa pubis, where each of them becomes a cylindrical tube, and unites with the other in the manner already faid. The heads or rounded extremities join the bafis,, of a diftindt body,’ called the glans, which is an expanfion of the urethra, and clofely united to it. , By the union of the corpora cavernofa from their roots to their round extremities or heads, a particular feptumj is formed by the tranfverfe fibres of both. Between the fibres of this feptum feveral fmall void fpaces are left, by which the corpora cavernofa communicate with each other. The urethra is the third fpungy tube which compofesthe penis, and it adheres to the corpora cavernofa through the whole length of the inferior groove formed by their union. It differs from the other two, both as it is oar*, rower, and as it forms a true hollow canal. Its fubftance is fpungy or cavernous, except a fmall portion next the bladder, and its inner and outer furfaces are membranous. It is at firft: no more than a membranous canal continued from the anterior opening of the bladder, at the place called the neck of the bladder About a finger’s breadth and an half from its origin, , it joins a cavernous fubftance like that of the two other tubes, only fmaller, which furrounds it through the whole extent of the inferior groove of the corpora ca-. vernofa. But before this fpungy fubftance begins to furround the tirethra, it forms a diftimft oblong body, like a pear or onion, which is connected only to the lower convex fide of the canal, and afterwards, being fplit on each fide, invefts it quite round. This body is called the bulb of the urethra, being larger than any other part of that canal, and divided interiorly* by a very fine membranous. feptum, into lateral parts; and therefore when it is inflated, it appears to be double or with two heads. The firft portion of the urethra, or that which is not covered by the cavernous fubftance, and which from the bladder to the bulb is only a membranous canal, is fitftained by a large folid whitifh mafs, of the figure of a chefnut, and fituated between the .bladder and the bulb of the urethra, its bafis being toward the1 bladder, the apex or point toward the urethra, and the fides lying upward and downward. This body is termed the proftates, from a greek word that expreffes its fituation before the veficulae feminales, and implies a plurality, becaufe it appears to be divided into two lateral lobes, by a hollow groove which runs through its upper fide from the bafis to the apex. The firft portion of the urethra lies in this groove, adhering very clofely to the proftates which furround it. The body of the proftates lies on the inteftinum rectum, and the apex is under the internal labium of the cartilaginous arch of the offa pubis. The inner fubftance is fpungy, but very compaft; and in each lobe there are feveral folliculi which open into the firft portion of the urethra, toward the bottom of the gropve. The fpungy fubftance. of the urethra, having reached the extremity of the corpora cavernofa, forms a large head, called the glans, which crowns the three Ijpungy pillars.