These bodies are full of cavities, which have all a communication with one another. The cavernous body of the _urethra_ continues from the _bulb_, near the neck of the bladder all along to the end of the _penis_, and includes the _glans_, or the nut of the yard; and is much of the same substance with the former. At the back of the _penis_, goes along the large vein, called the _vena penis_, which spreads itself all along into numberless branches that connect themselves with the ramifications of the arteries throughout all the cavernous bodies; and from thence is caused the erection, as I shall presently describe. The _glans_, or the nut of the yard, is remarkably delicate and sensible, as being the seat of pleasure in coition; it is also of a cellular substance, and in one continuation with the cavernous body of the urethra. Its sensation is greatly heightened by the _frænum_ being tied underneath, from the _præpuce_ to that part which keeps it, as it were, in an agreeable constriction when erect. The penis is allowed two pair, and a single muscle. The first pair is the _erectores_, which take their origin from the fleshy protuberances of the _ischium_, and lose themselves in the cavernous body of the penis. The second pair of muscles is the _transversales_; these take their rise near the forementioned, and fasten themselves at the root of the penis. The fifth is the _accelerator_, or the odd muscle; this muscle takes its commencement from the cavernous body of the _urethra_, and grasps the whole penis, and adheres to the _sphincter_ of the anus; the muscles aid and assist each other in the erection of the penis, which happens in the following manner: At the influx of the animal spirits, the _vena penis_, or the great vein in the penis is somewhat contracted, whence the blood is forced into the cavernous bodies of the penis and that of the urethra, as the reflux of the circulating blood from the arteries is hindered; hence, the cellulæ of the cavernous bodies are obliged to swell up and distend all the parts, and thus make the penis turgid and erect; when the penis is further titillated by the friction of coition, the parts become generally irritated to an agreeable constriction, whereby the seed rushes from the seed-bladders into the urethra, and is thus forcibly ejected in the time of ejaculation; then the whole fabric slackens, the constriction of the great vein relaxes, the blood regains its free circulation, and the penis becomes slack again. These are the faint out-lines of the genital parts; but to have a full description and comprehension of the peculiar properties of the genitals of both sexes, and also the sacred act of generation, I recommend to a serious perusal of the anatomical and physiological description of the genital parts of both sexes, in my _Treatise on the Venereal Disease_, where they will find a full and satisfactory account. -------------------------------------------