AIORBID CONDITIONS OF THE CELLULAR TrssuE.—As the cellular membrane is so in timately united with all other organs, it is very liable to be involved in diseases commencing. in these parts; but morbid action also very frequently arises primarily in this tissue. lt is subject to-1, inflammation, acute and chro nic, circumscribed and diffused; to the effects of inflamination, thickening and induration, si ippuration , ulceration, and mortification; 2, in filtration of blood, serum, air, and occasionally of other substances, as urine; 3, induration, occurring in new-born infants ; 4, morbid growths, such as fibrous productions, cysts, melanosis, scirrhus, vascular sarcoma ; 5, foreign bodies ; 6, preternatural increase or hypertro phy, and degeneration, or atrophy.
I. INFLAMMATION.—This tissue is very fre quently affected by inflammation, which may either present itself under the form of a distinct affection, as when it attacks the subcutaneous cellular membrane especially, or it may occur as a part of some other disease, as when inflam mation of the parenchyma of the lungs, liver, &c., spreads to the cellular tissue in which this substance is universally involved.
a. Acute circumscribed inflammation,orphleg 711011.—The anatomical characters of this form of inflammation of the cellular substance are essentially the same in whatever part of the body it may arise, either in the subcutaneous tissue, or in that part which penetrates into the interior of the various organs ; it will, therefore, be proper to trace the effects of it in a general manner.
I. Congestion of the bloodvessels.—The fects of irritation on the capillary vessels, in which the phenomena of inflammation are cipally observed, may be beautifully seen with the aid of a sufficiently powerful microscope in the transparent membrane of the frog's foot. After having familiarized the eye by ing the circulation for a short time, we shall that the first effect produced by the cation of an irritant is a distinct and evident acceleration of the blood's motion. I have not
been able to satisfy myself of that diminution of the calibre of the vessels which is said by some observers to accompany this acceleration. If the irritation be repeated, or if its power in the first instance were considerable, it will be seen after a certain time that the capillary ves sels become dilated, that the blood moves more slowly, and often that it oscillates and circulates apparently with difficulty ; its constituent parts become less distinct, the particles being crowded together. If the effects of the irritation now subside, the dilated vessels contract and recover their proper calibre, the blood again moves more freely, and the circulation regains its natural state; but, on the contrary, if the mor bid action still persists, the membrane begins to grow opaque, either in consequence of the engorgement of the vessels, or, as it has appeared to me, from an extravasation of one or other of the constituents of the blood ; or, lastly, the circulation altogether ceases, the vessels are further enlarged, the blood is stagnant, and is evidently deteriorated in quality, and the colour becoming deeper and deeper, is at length per fectly brown, or even black. This is the order in which the phenomena in the derangement of the circulation occur ; and although they have been more particularly studied in microscopical observations on the lower animals, yet many of them are daily to be observed in the human body during the progress of inflammation. Whilst the inflammatory action is confined to the first of the above stages, in which there is merely a preternatural excitement of the circu lation, it inay be arrested and put an end to without any further morbid change; and this may even happen in the second stage, where the blood, although accumulated and retarded in its motion, still circulates in its proper ves sels. This speedy termination of the disease has been called by the French writers deli tescence.