The mucous membranes receive a very great number of vessels. The remarkable redness that distinguishes them would be sufficient to prove it, if injections did not demonstrate it; this redness is not everywhere uniform. It is almost nothing in the sinuses of the face, in the internal ear, of which the membranes are rather whitish, and which appear so especially, because their extreme delicacy allows the bone upon which they are applied to be seen very distinctly. In the bladder, in the great intestines, in the excretories, &c. this colour, though still very pale, is a little more evident; it becomes very much so in the stomach, the small intestines, the vagina and in the pituitary and palatine membranes. In the gall-bladder we cannot distinguish it, because the bile always covers the mucous surface in the dead body. This colour depends upon a very extensive vascular net-work, the branches of which, after having passed through the mucous corion, and ramifying there, divide and spread ad infinitum on its surface, embracing the papillary body and covered only by the epidermis. It is the superficial position of these vessels and consequently their want of support on one side, that exposes them frequently to ruptures from considerable shocks, as happens on the surface of the bronchia from a severe cough, on that of the ear and the nose from a violent blow on the head. We know that hemorrhage of the mucous system bordering on the brain, is a common accident from concussions and wounds of the head. Hence why the least gravel makes the ureters bleed; why one of the signs of stone in the bladder is the passing of blood; why a blunt sound carefully introduced is so often withdrawn bloody from the urethra; why the least effort made with instruments carried upon polypi, into a fistula lachrymalis or into the nostrils, produces hemorrhage. I have already observed that we must carefully distinguish these hemorrhages from those furnished by the exhalants, and which do not suppose any vascular rupture. It is also the superficial position of the vessels of the mucous system, which makes its portions visible, as the red edge of the lips, the glans penis, &c. often serve to show us the state of the circulation. Thus in the different species of asphyxia, in submersion, strangulation, &c. these parts are remarkably livid, an effect of the passage of the venous blood, which has undergone no change from the want of respiration, into the extremities of the arterial system. The long continued exposure of the mucous system to the air, often makes it lose the redness that characterizes it, and it then assumes the appearance of the skin, as has been observed by Sabatier in treating of prolapsus of the womb and vagina, which, from this circumstance, have sometimes so misled some people, as to make them believe it a case of hermaphrodism.