Vesalius, who appears to have directed his attention to the particular nature of this struc ture in the penis, describes it as composed of innumerable fasciculi of arteries and veins closely interwoven, and included in an invest ing sheath.
Malpighi considered it as composed of diver ticula or appendicessof veins.
Mascagni, who at one time believed in the existence of cells interposed between the veins and arteries, in consequence of subsequent researches Aandoned that opinion, and de monstrated the fact, that a plexus of veins with arteries corresponding, but smaller and less numerous, formed the corpus spongiosum urethra; glans, and plexus retiformis, and that the arteries entering this substance terminated in the commencement of veins.
Mr. Hunter remarked that the corpus spon giosum urethre and glans penis were not spongy or cellular, but made up of a plexus of veins, and that this structure is discernible in the human subject, but much more distinctly seen in many animals, as the horse, &c.
Subsequent researches respecting the struc ture of the penis and clitoris of man, the horse, elephant, ram, &c. have been instituted by Duvemey, Mascagni, Baron Cuvier, Tiede mann, Ribes, Moreschi, Panizza, Beclard, Weber, &c. and the result has been a con firmation of the views developed by Vesalius, Malpighi, and Hunter.
Moreschi, in particular, has shewn that the corpora cavemosa penis, corpus spongiosum urethra', and glans consist of a congeries of fine vessels in all animals, whether covered by skin, hairs, spines, or scales; and that these vessels, which are principally veins, are characterized by their abundance, tenuity, and softness, which distinguish them from the veins in the muscles and other parts of the body.
The annexed figure (fig. 97) from Moreschi represents the plexiform arrangement of the veins apparent on the surface of the glans, and which empty themselves into the superficial veins of the penis.
Miller having more recently investigated the structure of the penis, has announced the discovery of two sets of arteries in that organ, differing from one another in their size, their mode of termination, and their use; the first he calls nourishing twigs (rani nutritii), which are distributed upon the walls of the veins and throughout the spongy substance, differing in no respect from the nutritive arteries of other parts; they anastomose with each other freely, and end in the general capillary network.
The second set of arteries he calls arteries hell rime. In order to see these vessels, an injection of size and vermilion should be thrown into a separated penis through the arteria profunda : when the injection has become cold, the corpora cavernosa should be cut open longitu dinally, and that portion of the injection which has escaped into the cells carefully washed out. If the tissue of the corpora cavemosa be now examined at its posterior third with a lens, it will be seen that, in addition to the nutritious arteries, there is another class of vessels of different form, size, and distribution. These branches are short, being about a line in length and a fifth of a millimetre in diameter; they are given off from the larger branches as well as from the finest twigs of the artery. Although fine, they are still easily recognised with the naked eye ; most of them come off at a right angle, and projecting into the cavities of the spongy substance, either terminate abruptly or swell out into a club-like process without again subdividing. These vessels appear most obvious and are most easily examined in the penis of man, to which the following description refers. These twigs branch off from place to place, sometimes alone, and• sometimes in little bundles of from three to ten in number; these, as well as the former, project constantly into the cells or venous cavities of the corpora cavernosa penis. When the arteries thus form a bundle, they arise by a common stem. Sometimes such a vessel, whether it proceeds from the artery as a single branch or as part of a cluster, divides into two or three parallel branches, which also either terminate abruptly, or else swell out near their extremity.
Almost all these arteries have this character, that they are bent like a horn, so that the end describes half a circle, or somewhat more. When such a branch so divides itself, there are formed doubly bent twigs inclined one to the other.