and this was the same during digestion as after that process was finished. From what has been said it appears, that if, whilst the stomach is empty, there is a reflux of blood to the omentum and spleen, it is less than has been commonly asserted. Moreover, during this state of vacuity, the numerous folds of the mucous membrane of this viscus leaving it, as we have before said, almost as much extent of surface, and consequently of vessels, as during its plenitude, the blood must circulate there nearly as freely as when the viscus is in a contrary state; it has therefore no real obstacles; the only impediment is in consequence of the tortuous direction the vessels are then thrown into. Now this obstacle is easily surmounted, since the vessels suffer no constriction or diminution of calibre by the contraction of the stomach. 51. As respects the other hollow organs, it is difficult to examine the circulation of their adjacent viscera during their plenitude or vacuity; for their vessels are not superficial, as in the omentum, or insulated, as in the spleen; therefore, to decide this question concerning them, we can only observe the state of the mucous membranes upon their internal surface. Now they have always appeared to me as red during the contraction as during the dilatation of the organs. Finally, I give this only as a fact, without pretending to draw any inference from it opposed to the common opinion. It is, in fact, possible, that though the quantity of blood be always nearly the same, the rapidity of the circulation may increase; and consequently, in a given time, more of this fluid will be sent there during the plenitude of the viscera. This appears to be necessary for the secretion of the mucous fluids, which are then more abundant. SECTION VI. OF THE VARIATIONS IN THE ORGANIZATION OF MUCOUS MEMBRANES IN DIFFERENT REGIONS. 52. The assemblage of the epidermis, corps papillaire, chorion, glands, and vessels, constitutes in the mucous membranes their intimate organization, which presents very considerable variations in the different regions in which they are examined. I shall point out only the principal of them; for in no different parts do these membranes present the same appearance, and in order to describe all their differences they should all be examined.