Mr. John Hunter has however pretty clearly demonstrated that the vesiculz are not intended to contain semen, but that they secrete a peculiar fluid, to sub serve the purpose of generation. See his " Observations on certain parts of the Animal Economy." Prostate gland—The origin of the ure thra is surrounded by the substance of this gland, which in,size and form much resembles tie cheanut Numerous open ings are found in the commencement of the urethra, which discharge on pressure a whitish viscid fluid ,secreted in the sub substance of the pstate. A portion of the gland projects into the lower part of the commencement of the urethra, and has received the name of caput gallinagi nis : it is on this that the openings of the canals, formed by the junction of the visa deferentia and vesicular serninales are found.
The urethra is subservient to two pur poses; the expulsion of the semen in the act of copulation, and the conveyance of the urine from the bladder. Its surface is perfectly smooth, and is covered and pro tected by a mucous secretion. The dia meter of tins canal varies shg" at dif ferent parts, but may be stated generally at about one-olihth of an inch. At its first departure the bladder, it is surrounded for one inch by the prostate; it is then continued as a simple membran ous tube, but surrounded by fibres for another inch ; this is called the membranous portion of the urethra. in the rest of its passage it is surrodided by a vascular substance, called corpus spon gictsum ; this is accumulated in a consi derable mass at its commencement, where indeed the urethra is broaderthan in any other sitilation, and this is called the bulb. The seminal and proStatic liquors are poured into the bulb of the urethra, and are forcibly expelled from thelce by a sort of convulsive contraction o a muscle, whose fibres surround this part of the canal; the ejaculator seminis.
The glans peqls is nothing more than a portion of the same vascular mass, which surrounds the rest of the urethra, cover ed by a very delicate, sensible, and finely organized integument.
The bulb, corpus spongiosum, and glans, are susceptible of the same erec tion as the body of the penis; which is indeed essential to 'the performance of their functions, in conveying Ole fecun dating liquor into the body of the female.
The penis consists of two bodies, call ed crura, or corpora cavenosa, which arise separately from the &Ones of the pelvis; but join so as to form afterwaids a single organ. Each ems consists of a very strong and detise ligamentous tube, filled internally with cellular substance, into the cells of which the arteries open, and from which the veins commence. The arteries pour the blood into these organs with great energy, in obedience to the passions of the mind, and thereby distend the ligamentous tubes until they feel perfectly hard and rigid, in which state the whole organ is fitted for the function which it Ita.s to perform in the act of copulation. The urethra, sur rounded by its spongy substance, runs along the under surface of the corpora cavernosa, and the glans penis is situated at the anterior extremity of these parts.
The body of the penis is covered by coinmon integuments,which, being adapt ed to cover the organ in its extended state, fall into wrinkles when it is col lapsed. These axe continued beyond the end of the glands, and are inflected, so as to form a hood or covering to the glans, called the prepuce. 'Ile latter part is connected to the mouth of the urethra by a small fold named the frenum. The surface of the glans, and the lining of the prepuce, are smeared with art unctu ous matter of peculiar odour, furnished by some small glands.