Function of the prostrate gland.— It is the office of the prostate to secrete a bland and somewhat viscid fluid, which is poured into the urethra at the commencement of its course, at that point where the secretion of the testes and vcsiculm seminales are re ceived into the canal. It is well known that the secretion of the prostate is in creased in quantity under states of venereal excitement ; I have, however, some doubts as to whether the secretion effused under such circunistances is wholly prostatic : I cannot help thinking that some of it at least is due to the glands of Cowper and the follicles of the urethra generally ; but, be this as it rnay, there can be no doubt that the largest quantity of the prostatic fluid is poured into the urethra at the moment of, or prior to, the venereal orgasm ; at least we are justified in drawing this inference from observations made on these parts in animals killed during, or immediately after, the completion of the act of copulation.
That the prostatic fluid is subservient to the generative function, may be deduced from these circumstances ; and this is further esta blished by the fact mentioned by Hunter, that the gland is liable to changes at certain sea sons, and that in the mole, in winter, the prostate is scarcely discernible, whilst in the spring it becomes of large size, and filled with fluid. We are not aware whether this is the case universally in the animal kingdom. How does the prostatic fluid aid the function of generation ? An old opinion assigns to these accessory glands the office of perfecting and increasing the bulk of the seminal secretion, so that the urethra may be more fully distended by it, and its muscles may be enabled to act more com pletely in forcibly injecting its contents into the vagina. This idea is, in my mind, rather too mechanical, although it may be advanced in its favour, that these accessory glands are found in all animals, where they exist, to empty themselves into those dilated portions of the urethra, in which the seminal secretion is supposed to accumulate prior to its expulsion. It has been thought by some that the pros tatic secretion is useful in diluting the semen, so as to increase its bulk, not merely for the more perfect distension of the urethra, but that it may ensure the more easy transmission of this secretion into the feniale vagina, and thus favour its contact with, and impregnation of, the ovum. As to its defending the orifices of the ejaculatory ducts from the presumed acrimony of the urine, I cannot attach any importance whatever to this notion ; the gland is essentially a sexual organ, and its use must, in some manner or another, be con nected with the excretion of the seminal fluid, either in the nianner just mentioned, or in lu bricating the surface of the urethra, so as to facilitate the onward passage of this fluid.
The very structure of the prostate, which is of the simple follicular character, favours the latter notion. Its position at the commence ment of the urethra leads to the same conclu sion. It is probable that its secretion is poured into the urethra prior to the escape of the seminal fluid into the canal ; and it is quite evident that no large glandular masses could have been conveniently placed along the urethra in any other situation ; for however much they vary in number and size, in the various orders of animals, their position near the beginning of the urethra is constant.
The prostate gland, with Cowper's glands and the vesiculm seminales, must be regarded as accessory rather than as organs essential to the generative function. That it is not essential in man, is rendered probable by the persistence of the procreative faculty in many cases of extensive disease of this organ.
In connection with this obscure and diffi cult subject, I think the fact of the prostatic secretion being naturally-, as I believe, acid, is a circumstance of sonne interest. The secre tion of the testes is well known to be alkaline, and has a strong tendency to coagulate or become inspissated. Is it not probable that the reaction of the prostatic on the seminal fluid may be of use in the maintenance of the fluidity of the latter ? The idea is somewhat confirmed by the fact, that in women the acid secretion of the vagina prevents the coagu lation of' the menstrual blood, and thus favours its discharge. This has been proved by Mr. Whitehead, who found that, if the menstrual fluid was received directly from the os uteri into a speculum, it coagulated like ordinary blood.* Morbid Anatomy.— Hypertrophy. — In ad vancing years, when all other structures in the body begin to show evidence of a fail ing nutrition, and are atrophied or wasted by interstitial absorption, the prostate gland, on the contrary, very frequently becomes the subject of a remarkable increase in size. This is so common after the age of fifty, that an enlarged prostate may be alinest regarded as one of the necessary contin gencies of advanced age. It is not, how ever, exclusively in the old person that this takes place ; it sometimes happens at a much earlier period of life ; nay, a case is men tioned by Sir Astley Cooper of a boy whose prostate was found, on dissection, of very large size ; but it is not improbable that this remarkable enlargement depended on stru mous deposit in the gland. In considering this su*ct, it is important to distinguish between this affection of the prostate and the simple engorgement consequent on acute or chronic inflammation ; these latter conditions occur more frequently between twenty and forty years of age, and depend on stricture of the urethra, or the mal-treatment of severe gonorrhcea.