325. I had intended to treat of the circulation of the humor and serosity through the cellular tissue of the peritonaeum, and of its sources and places of discharge; but inasmuch as the foregoing experience has hitherto afforded me no clear and distinct ideas upon the subject, therefore I dare not venture to determine anything with certainty. However, I see plainly enough, that the fluid which irrigates and sometimes inundates the cellular tissue of the peritonosum, comes originally from no other source than the viscera enclosed in the cavity of the abdomen; and that the stream is constantly circulating through the whole of the cellular tissue; and never escapes from its cells or follicles into the cavity itself, unless they are ruptured by over distention, or by the wearing out of their membranous partitions; but rather that the peritonaeum absorbs the fatty effluvial vapor with which the cavity of the abdomen abounds, and carries it in a determinate channel, with the rest of its serosity, to some place of discharge, which place I have (in Chap. XIV.) maintained to be situated at the kidneys.
FIRSTLY; That the fluid which irrigates and sometimes inundates the cellular tissue of the peritonaeum, comes originally from the abdominal viscera themselves that is to say, from the stomach, intestines, liver, and other viscera, according to the nature of their communication and operation. This is proved by the cellular tissue of these viscera, by their sometimes having two cellular tissues, one above and one below their muscular membranes; and by their continuity, the continuity of the external cellular tissue particularly, by means of foramina, with the innermost membrane of the viscus; and by its immediate communication with the cellular tissue of the peritonaeum: which latter circumstance is proved by the abundance of serous liquid which comes to the surface [of the viscus], where all but the purer portion, (which is absorbed by the numerous lymphatics,) is committed into circulation through the peritonaeum. The free continuation of this cellular tissue from the livet and intestines to the peritonaeum, is pretty evident, not only from ordinary anatomy, but also from artificial anatomy, as pursued by injections; for when the cellular tissue of the one is distended by inflation, the adjoining part of the tissue of the other swells. This is likewise abundantly shown in tympanitis, ascites, dropsy, and other inundations: and we also see clearly, that the quantity of wind and water in these diseases cannot have any other source than the viscera themselves, where the air is disengaged in great quantities in consequence of the disruption of the solid parts; and the viscera, as the stomach, the small and large intestines, and the liver, are inundated with a constant torrent of water.
SECONDLY; That this stream circulates through the whole of the cellular tissue. This proposition, being a consequence [of the preceding proposition], admits of no doubt whatever. For granting the continuation of the cellular tissue through the peritonaeum, and granting the constant agitation of it by the muscles, consequently the expansion and constriction, the inevitable result must be, that the fluid circulates whither the tissue is permeable, and is determined to certain places of discharge; it cannot stagnate, without producing the destruction of the whole.
THIRDLY; That it never escapes from the cells or follicles into the cavity of the abdomen, unless the membranous partitions are ruptured by over distension. This is fully proved by the above-mentioned morbiti swellings of the peritonaeum, as tympanitis, in which the abdomen is turgid with air; ascites, when the cells are distended with water till they resemble hydatids; and particularly dropsy of the peritonaeum. For if the internal coat of the peritonaeum were pervious into its general cavity, or perforated by little foramina leading thither, then no dropsical stoppage of the kind could thus augment the peritonaeum with respect to mass and thickness, but the wind or water would escape immediately through the porous pellicle, and fill the cavity. The same thing may be shown artificially by the injection of air or water, which distends the cellular tissue, but is not found to escape elsewhere: exactly as in the corresponding coat of the omentum, which like the peritonaeum has numberless pores, (so some anatomists have observed,) and yet no evaporation takes place from its little cellular cavities. "When we handle these membranes [of the omeutum]," says Winslow, "with dry fingers, the membranes stick to them so closely as hardly to be separated without being torn; as we see by the reticular holes that appear in those portions of the membranes that have been thus handled. In that case it is to no purpose to blow through the orifice already mentioned [the foramen of Winslow]; and it is owing to these small accidental holes that the membranes of the omentum have been supposed to be naturally reticular" (n. 252).
FOURTHLY; That the peritonaeum rather absorbs the fatly effluvial vapor with which the cavity of the abdomen abounds. For wherever any vapor or humor is present, and indeed supplied in a continual stream, there must necessarily be places of discharge provided; consequently from the cavity of the abdomen, as from all the other cavities. Whether the discharge takes place from this cavity by any external prolongations, as for instance, towards the scrotum, or along the ischiadic vessels, or elsewhere, is a subject for enquiry; also, whither the humors go next after leaving those places. Experience clearly shows, that the peritonaeum throughout is full of perforations, and that the foramina afford no passage either for air or liquid into the cavity from the cells outwards. Granting, then, the existence of little foramina, (like those of the omentum, according to the observation just quoted,) and the possibility of their being bibulous and attractile, and the converse follows as a matter of course, namely, that this membrane is permeable from the cavity into the cells of the cellular tissue. The surface of the internal membrane of the peritonaeum, according to Winslow, "is continually moistened by a serous fluid discharged through almost imperceptible pores. These pores may be seen by spreading a portion of the peritonaeum on the end of the finger, and then pulling it tight on all sides; for then the pores are dilated, and small drops may he observed to run from them, even without the microscope. The sources of this fluid are not as yet well understood" (in. 310).
FIFTHLY; That the peritoneum conveys this serosity in a determinate channel, to some place of discharge; which place I have maintained to be situated in the kidneys; and during the uterine state, in the renal capsules. See the Chapters on the Kidneys and Succenturiate Kidneys. The greatest care seems to be taken, to prevent the intestines from communicating with the urinary bladder, through the cellular tissue of the peritonaeum, and the more pure and chyliferous portion of the serum from thus entirely escaping by a short cut once allowed to be opened, along with the worthless and aqueous portion. Hence the passage intervening between them, as for instance, about the concentration of the abdominal muscles, is comparatively narrow and constricted. But if we attentively consider the structure of the bladder, it will appear very probable, that the bladder itself does imbibe some part of the thin vapor, although relatively to the whole, a very small part, and like the rest of the viscera, throws it out into its cellular tissue, as into the surrounding peritonaeum, and perhaps around the ureters.
