45. The mucous membranes receive a great number of vessels: the remarkable redness which distinguishes them would be sufficient to prove it to us, if it could not be demonstrated by injections. This redness is not everywhere uniform; it is less in the bladder, large intestines, and frontal sinuses; very marked in the stomach, small intestines, and vagina, &c. It is produced by a web of very numerous vessels, whose supplying branches, after having passed through the chorion, finish on its surface by an infinite division, embracing the corps papillaire, and is covered only by the epidermis. 46. It is the superficial position of these vessels that frequently exposes them to hæmorrhages, as we remark principally in the nose, and as is seen in hæmoptysis, hæmatemæsis, hæmaturia, in certain dysenteries, where the blood escapes from the parieties of the intestines, in uterine hæmorrhages, &c.; so that those spontaneous hæmorrhages, which are independent of any external violence applied to the open vessels, appear to be special affections of the mucous membranes; they are seldom observed but in these organs, and they form at least one of the grand characteristics which distinguishes them from all the other membranes. 47. It is also the superficial situation of the vascular system of mucous membranes that renders their visible portions, as on the lips, the glans, &c.; serviceable in showing us the state of the circulation. Thus, in various kinds of asphyxia, in submersion, strangulation, &c., these parts present a remarkable lividity; the effect of the difficulty that the venous blood finds in passing through the lungs, and of its reflux towards the surfaces where the venous system arises from that of the arteries. 48. I have already observed in the fœtus, and newly born infant, that the vascular system is as apparent in the cutaneous organ as in the mucous membranes; that the redness is there the same; it is even in that part more marked in the earlier periods of conception; but soon after birth all the redness of the skin seems to concentrate itself upon the mucous membranes, which before, being inactive, had no need of so considerable a circulation, but which, becoming all at once the principal seat of the phenomena of digestion, of the excretion of the bile, of the urine, of the saliva, &c., demand a larger quantity of blood. The long continued exposure of mucous membranes to the air frequently occasions them to lose their characteristic redness, and they then assume the colour of the skin (as M. Sabattier has well observed in treating on prolapses of the uterus and vagina). By this circumstance some have been deceived in believing such instances to be cases of Hermaphrodism.