78. The intestinal juice, that Haller has particularly considered, but which appears to be less in quantity than he had estimated, the gastric juice, and that of the œsophagus, are very probably disposed of by way of exhalation on their respective mucous surfaces; but in general it is very difficult to distinguish with precision, in these organs, what belongs to the exhalent system from what is furnished by the system of mucous glands, which, as we have said, are everywhere subjacent to them. Thus we constantly see the mucous fluids of the œsophagus, stomach, and intestines, mix themselves with the other fluids of these parts. 79. That mucous membranes absorb is evidently proved by the absorption of the chyle upon the intestinal surfaces, of venereal virus upon the glans and urethra, of variolous poison which is sometimes rubbed upon the gums, of the serous portions of the bile, of the urine, and of the semen, when they remain in their respective reservoirs. When, from paralysis of the fleshy fibres which terminate the rectum, the fæces accumulate at the extremity of that intestine (a very common case in aged persons, and of which Desault has cited many instances), these accumulations frequently become hard, probably from the absorption of their juices, which are obstructed there. We have many cases in which the urine has been almost entirely absorbed by the mucous surface of the bladder, when there has been absolute obstruction in the urethra. Whatever may be the mode of this absorption, it appears that it is not performed in a constant, uninterrupted manner, like that of the serous membranes, in which the exhalent and absorbent systems are in a continual alternate action; but that it occurs only under certain circumstances, of which perhaps the greatest part are not in the natural order of the functions. Finally, we have yet fewer data respecting the mode of mucous absorption than on that of cutaneous absorption: we confess it is very little understood, and many even question its existence. SECTION X. REMARKS ON THE AFFECTIONS OF MUCOUS MEMBRANES. 80. It is not my design to examine the affections of mucous membranes; I shall notice only some phenomena, which in these affections I believe deserve a particular attention, and the explanation of which I propose to physiological physicians. 81. Why do mucous membranes seldom contract adhesions from inflammation, since that occurs so frequently in serous surfaces under the same circumstances? Why does not the internal surface of the inflamed stomach, intestines, or bladder, adhere in its various portions like the pleura, tunica vaginalis, testis, &c. 82. Why, in inflammations of mucous membranes, is there an abundant flow of that fluid which habitually moistens them, and which constitutes the different kinds of catarrhs, whilst the source of the fluid that exhales from serous membranes is generally dried up in analogous cases?