One of these surfaces, intimately united to the organ, appears to send various elongations into it, which identify at first view its existence with that of the membrane. Many fibres detached from the albuginea, from the covering of the corpus cavernosum, from the peculiar tunic of the spleen, &c. or rather adhering to these tunics, penetrate the respective organs of these membranes, and crossing there in various directions, form as it were the outline and frame, around which are arranged and supported the other constituent parts of these organs, which seem from this to have the external membranes for a mould; as we see when these moulds are removed, irregular vegetations shooting up here and there. The callus, in displacements too great to allow the periosteum to extend over the divided surfaces, is rough and uneven. The form of the testicle alters, when the albuginea has been divided at any part. This adherence of the fibrous membrane which covers different organs, to the internal elongations of these organs, and the fibres which compose their outline, has made anatomists believe that the nature of one was the same as that of the others, that these were but elongations of the membrane. I thought so when I published my Treatise on the Membranes; but new experiments have since convinced me of the contrary. I am confident that the membrane of the corpora cavernosa belongs to the fibrous system alone. The internal spongy texture, contained in the cavity of this membrane, has not the nature of it, is not as all anatomists say an elongation of it. The spongy texture is not made by laminæ, which, according to the common expression, are detached from the membrane and produce it by their interlacing. This is a separate body, unlike in its life and its properties. By exposing a corpus cavernosum to ebullition, I have evidently observed this difference; the external membrane does, like all the fibrous organs, become thick, yellowish, semi-transparent, then melts more or less into gelatine; the spongy texture, on the contrary, remains white, soft, does not increase in size, hardly crisps at all from the action of fire, exhibits, in a word, an appearance which I can compare to no texture treated in the same way by ebullition. Maceration also answers very well to distinguish these two textures. The first yields but slowly to it; its fibres remain a long time distinct; they have still their natural arrangement, when the second is already reduced to a homogeneous, reddish pulp, in which nothing fibrous, nothing organized can be any longer traced. In general, it appears that the spongy texture of the corpora cavernosa is their essential part, that in which the great phenomena of erection take place, that which animates the peculiar kind of mobility which distinguishes it from the other organs. The fibrous shell is only accessory to its functions; it is but a covering; it is only formed to obey in erection the impulse which is communicated to it.