Yet even in these states the fat of the animal body is seldom entirely wasted. In several organic diseases, in which great emaciation takes place, a considerable quantity of fat is always found in the orbits behind the eyeball, round the substance of the heart, around the kidneys, in the colon, and in the mesentery and omentum. Thus one or both lungs may be extensively occupied by tubercles and indu rated portions giving rise to the-usual symptoms of pulmonary consumption terminating fatally, yet without removing the fat from the subcuta neous layer of the chest and belly ; and in various organic affections of the brain espe cially, a considerable quantity of fat is found, not only in the subcutaneous layer, but at the outer surface of the serous membranes.
According to the observations of William Ilunter, anasarcous dropsy is the only disease in which the fat of the adipose membrane is entirely consumed. " This disorder, when in veterate, has that effect in such a degree, that we find the heart or mesentery in such subjects as free from fat as in the youngest children." This, however, is in some degree denied by Bichat, who contends that it is not uncommon to find much subcutaneous fat in subjects greatly infiltrated.* It is obvious that much will depend on the stage of the disease. It cannot be expected that the moment serous infiltration appears in the filamentous tissue, all the fat should be at once removed from the adipose. The process of absorption is gradual as is that of deposition ; and the infe rence of Hunter may be regarded as nearly exact in reference to long-continued, or what he terms inveterate dropsy. It is certain, that while it is very difficult to deprive the bones of ordinary subjects of oil, those of dropsical sub jects are the only ones which it is possible to obtain free from this substance.
In certain diseases, especially those the ter mination of which is attended with serous effusion into the cavities of the serous mem brane, the fat is partly absorbed or may be converted into a sort of sero-gelatinous fluid. In chronic dysentery, for example, the subcu taneous fat and that of the heart and omentum, in a great measure disappear, while in their place we find effused an orange-yellow coloured sero-albuminous fluid, of a jelly-like aspect, which coagulates on the application of heat or the addition of re-agents. In the bodies of those, also, cut off by scirrhous disorganization or cancerous ulceration, the greater part of the fat is in like manner absorbed, and in its place appears a dirty orange-yellow coloured sero albuminous fluid.
The removal of the fat from its containing membrane is effected by the process of absorp tion, the agents of which are supposed by William Hunter, Portal, Bichat, and Mascagni, to be the lympathics. According to the results
of the experiments of Magendie, Mayer, Tiede mann and Gmelin, Segalas and others, it must, in some measure at least, be ascribed to the in fluence of minute veins. It is a point of some interest to know in what form it is absorbed, whether as oily matter, or after undergoing a process of decomposition The observation of Dr. Traill, above quoted, would lead to the former view; but it is not easy to conceive that this should be uniform. We want, in short, correct facts on the point at issue.
5. Adipose sarcoma.—This consists in an un usual deposition of firm fatty matter in cells, the component fibres of which are sufficiently firm to give it consistence. The tumour, which is generally globular, is always surrounded by a thin capsule, formed by the condensation of the contiguous filamentous tissue. The tumour is supplied by a few bloodvessels, which pro ceed from the capsule, but which form so slender an attachment that they are readily broken, and the tumour is easily scooped from its seat. This sort of tumour occurs almost invariably in the adipose membrane, and seems to consist in a local hypertrophy of the part in which it is found. It may have a broad basis, but is often pendulous, or attached by a narrow neck or stalk. It is the most common form of sarcomatous tumour, and may occur in any part of the body in which there is adipose mem brane, but is chiefly found on the front and back of the trunk, and not unfrequently on two places at the same time.
6. Steatoma.—In adipose sarcoma the adi pose matter is deposited in cells, and the tumour derives a degree of firmness from the fibres with which it is thus traversed in every direction. In other instances, however, the adipose matter is deposited in a mass in the, cavity of a spherical or spheroidal cyst, formed in the filamentous or adipose tissue ; and the tumour is soft and compressible, and seems to contain fluid or semifluid matter. When cut open it is found to contain a soft semifluid matter of the consistence of honey, but of oily or adipose properties. In such circumstances the inner surface of the cyst, or at least the vessels of this surface, are the agents which secrete the fatty matter. This tumour may occur either in the filamentous or the adipose tissue, but is to be regarded as an example of local deposition of adipose matter. It may appear in any region of the filamentous tissue, but is most frequent about that of the head and face. Small steatoms are not unfrequent in the eyelids and in the scalp. Larger ones are more frequent about the neck.