Xavier Bichat

“ Besides the three strata, which we have just mentioned, the mucous membranes present in their structure a great number of glands and blood vessels. The mucous glands exist in all membranes which bear that appellation: they are situate under their chorion, and even in its substance: they continually discharge, through imperceptible orifices, a mucilaginous fluid, which lubricates their free surface, and defends it from the impression of the bodies with which it is in contact, at the same time that it facilitates the passage of those substances. ”

“ That in the stomach this vascular web exhales the gastric juice, and in the intestines it is interlaced with the origin of the absorbents, so that they embrace the villosities, are facts that we must admit, after the experiments and observations of the anatomists, who in these times have been engaged with the lymphatic system: but that does not contradict the assertion, that the bases of these villosities are nervous, and perform the same functions only on the mucous membrane as the papillæ do on the cutaneous organ. ”

“ It is very difficult to point out with precision the character of the tonic powers of mucous membranes, because, being almost in every part united to a muscular layer, we can hardly distinguish what belongs to the tonicity of the one from what depends upon the irritability of the other; or otherwise, if the mucous membranes be isolated, as in the nostrils, yet their attachment renders the phenomena of their tonic powers very obscure. ”

“ What I say is so true, that if in the interior of the organs the mucous membranes be in contact with a foreign body differing from that which is habitual to them, they [79] transmit the sensation of it to the mind; instruments introduced into bladder or stomach are examples of it. Fresh air, which in very hot weather is suddenly introduced into the trachea, causes an agreeable sensation over the surface of the bronchi; but from habit we soon become insensible to it, and the perception ceases. ”

“ OF THE EXTERIOR ORGANIZATION OF MUCOUS MEMBRANES.
8. Every mucous membrane presents two surfaces; the one adhering to the adjacent organs; the other free, beset with villosities, and always moist with a mucous fluid: each of them deserves a particular attention.
9. The adherent surface is attached to muscles almost throughout its extent. The mouth, the pharynx, the whole of the alimentary canal, the bladder, the vagina, the uterus, and part of the urethra, &c. present a muscular bed, embracing [10] the exterior of their mucous coat. ”

“ However, it is difficult to decide the question by ocular observation; the tenuity of these prolongations conceals their structure even from our microscopic instruments, a kind of agents by which physiology and anatomy do not appear to me in other respects ever to have obtained great assistance, because when parts are so viewed each person sees in his own way, and is impressed accordingly. ”

“ I distribute the sympathies of mucous membranes, like those of most of the other organs, into three general classes. In the first class are ranked the sympathies in which irritation, on one part of the mucous surface, produces a sensation in a distant part. A stone in the bladder occasions pain at the end of glans; worms in the intestines excite an itching at the nose. ”

“ Whilst the stomach is in a [59] state of repletion its vessels are more apparent on its exterior surface than during its vacuity; its mucous surface at this time has no higher degree of redness, but it has sometimes appeared to me to be less red than when the viscus was empty. (2) The omentum, being less extended during the plenitude of the stomach, presents nearly the same number of apparent vessels, equal in length, but more folded upon themselves than during the vacuity of that organ [C] . If they are then less [60] loaded with blood the difference is scarcely perceptible. ”

“ Others, not less important, demonstrate the reciprocal dependence in which the skin is found with the same membranes, as respects their vital powers. (1) During digestion, when the mucous fluids are poured out in abundance into the stomach and intestines, when, consequently, the mucous membranes of the alimentary canal are in high action, the fluid of insensible perspiration is evidently diminished, according to the observation of Santorius: it is very small in quantity three hours after a meal, so that the action of the cutaneous organ is visibly less energetic. ”

“ The mucous membranes, by the continual secretion of which they are the seat, perform a principal part in the animal economy. They are to be regarded as one of the grand emunctories, by which the residue of the nutriment constantly escapes from the body ”

“ On the contrary, at the origins of mucous membranes exciting agents vary every instant: the mind can, therefore, perceive their presence, because it is able to establish relations between their various modes of action. ”

“ It should seem, that in situations where these glands escape our observation, nature makes up for their tenuity by increasing their number. In the lower animals, particularly in the intestines, they form by their number a kind [39] of new layer, in addition to those we have described. The same may be observed in the palate, velum, &c. in man.
36. There is therefore this great difference between mucous and serous membranes; that the fluid which lubricates the former is furnished by secretion, whilst that which moistens the latter is produced by exhalation. ”

“ In examining the skin of a Negro with attention, the epidermis being detached, I have seen the external surface of the chorion tinged with black, and that was all. Further, whatever this corpus mucosum may be, it certainly does not exist in mucous membranes, since they do not participate in the colour of the integuments. The heat of the sun, which darkens these in white people, does not appear to act upon the commencement of these membranes, which are equally exposed with them to its influence, as is seen in the red borders of the lips, &c. ”

“ Remark the fact, that none of the mucous fluids enter into the circulation, but are thrown out externally; that of the bladder, ureters, and urethra, with the urine; that of the vesiculæ seminales [49] and of the vassa defferentia with the semen; that of the nostrils by the action of blowing the nose; that of the mouth partly by evaporation, and partly by the anus with the excrements; that of the bronchi by the pulmonary exhalation, which is effected principally by the solution of this mucous fluid in the air of respiration ”

“ In fact, the instant when an odour enters the nose, having the air for its vehicle, it cannot at once pass into the sinuses, because the orifices by which these cavities communicate with the nose are very small ”

“ Inflation with nitrous gas is always mortal, and its contact appears to strike the muscles with atony. The stomach distended with it very soon loses its power of contracting, and its folds disappear. Here, as in all the experiments which have the vital powers for their object, we frequently obtain very variable results.
16. It follows, from what we have said respecting the folds of mucous membranes, that in the contraction of the hollow organs, which are lined by them, they suffer but a very trifling diminution of surface, they scarcely contract at all, but fold themselves within ”

“ On the contrary, during, or immediately after digestion, it is more clear, mild, and less irritating; there must, therefore, be, during digestion, another stimulus: now this stimulus is the aliment passing over the mouth of the ductus communis choledochus [A] . ”

“ Their number, at the first view, appears very considerable; for the organs within which they are reflected are numerous. [2] The stomach, bladder, urethra, uterus, ureters, the intestines, &c., borrow from these membranes a part of their structure: nevertheless, if it be considered, that they are continuous throughout, that everywhere they are observed to be extended from one organ to others, arising, as they did at first, from the skin, their number will appear to be singularly limited. ”

“ The sudden suppression of the functions of the cutaneous organ often determines a morbid increase of action in those of the mucous membrane. Cold air, which checks the perspiration, frequently produces colds and catarrhs, affections which are marked by the sensibility and increased action of the mucous glands. (4) In various affec [73] tions of the mucous membranes, baths, which relax and determine to the skin, produce beneficial effects. ”

“ For, as we have said, these glands are always subjacent to the membrane, and [42] are consequently separated by it from the irritating bodies. It appears that the above fact belongs to a general modification of the glandular sensibility, which is susceptible of being put into action by every irritation upon the extremities of the excretory ducts, which will be proved by the following considerations: (1) The presence of food in the mouth produces a more abundant flow of saliva. ”

“ 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 ”

“ That these variations distinguish them from serous membranes, whose aspect is everywhere the same, as may be seen by comparing the pericardium with the peritoneum, &c. (2) The sensibility of mucous membranes varies in a very peculiar man [69] ner in their different portions: thus an emetic irritates the stomach, but not the conjunctiva; the pituitary membrane perceives only odours; the mucous surface of the tongue flavours, &c. On the contrary, the contact of all kinds of bodies with the naked serous membranes produces phenomena exactly analogous. ”

“ Erudite, observant, and industrious, he, at an early age, reared a monument of science, which will perpetuate his name and matchless talents. From the rich treasures he has left, the Translator presumes to present this Treatise in an English costume. Where all is excellent it is difficult to make a satisfactory selection ”

“ I think, that from what occurs in the intestines we cannot infer what takes place in the pituitary and palatine membranes, &c.; because, although analogous, [90] their organization may be different. In these parts we cannot examine the venous blood returning from them, as in the intestines: but, (1) If we consider, that in animals, which have for some time respired oxygen gas, the mucous membrane of the fauces does not exhibit any increase of redness ”