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.
SECT. VIII.
Of the Skin.
The whole human automaton is covered with a skin, the mechanism of which is not less curious than what we have already described.
It is a texture curiously interwoven with an infinite number of tendons, arteries, veins, nerves, and lymphatic vessels. The tendons form the net-work of the whole, and give it an elasticity, from whence it requires a muscular motion; and the rest add each their parts, as I shall hereafter describe.
The skin, universally over the whole body, is divided into three parts; but in most parts it is found to have four.
The external, is the cuticula, or scarf skin; this is a horny and insensible substance, formed by nature as a shelter for the next part of the skin, which is exceedingly sensible; on examination it appears to be a horny substance, and as it were, little scales continued from the immediate skin, which on any external injury, such as repeated friction, fire, scalding, or blistering, separates from the main skin. The next is the real skin, called cutis; This is strongly interwoven with tendinous and nervous fibres, interspersed with numberless ramifications of arteries, veins, and lymphatic vessels; whence it is not only exquisitely sensible, but elastic, and on the least injury, subject to bleed. On the external surface is a very thin plexus, called the reticulare; which has the tinge of the natural hue of the skin, and distinguishes the complexion of the negro, the tawny, and white, from each other.