7. Lipoma.—This name was first applied by Littre to a wen or cyst, filled with soft matter, possessing the usual properties of ani mal fat. The matter of steatom, according to this surgeon, is either not or imperfectly in flammable, by reason of its degeneration or commixture with some other animal secretion. The propriety of this distinction has been de nied by Louis and others, who maintain that these tumours differ in nothing, unless per haps in degree. It has been favoured, never theless, by Morgagni, and adopted by Plenck, Desault, Bichat, and various foreign surgeons, and is defended by Boyer, who represents the steatom as differing from lipoma in the matter being white, firm, and changed from its origi nal character, and in possessing the tendency to degenerate into cancer. Plenck had previ ously distinguished the lipoma by its being destitute of a cyst, a circumstance not required by Littre.
Though thus admitted to differ, the anato mical character, as given by Morgagni, and confirmed by Boyer, is in both nearly the same : a cyst, containing unchanged fat, or granular adipose matter, in cells formed by the original fibres of the adipose membrane, ac cording to Morgagni, or those of the filamen tous tissue, according to Boyer. At the base or stalk, in the case of pendulous steatom, the cells are compressed, but loose in the body of the tumour.
This description, with the alleged cancerous tendency, accords more with the characters of the adipose sarcoma than those of the genuine wen. Personal examination enables me to say, that, in the case of small steatoms of the scalp, eyelids, face, &c. no fibres of this kind are re cognized ; and to such, if any distinction be adopted, the name of lipoma should be con fined. In the case of such larger steatoms as I have seen in other regions of the body, though the contents are firmly connected together, and some filamentous threads may be seen here and there, or the tumour may even be separa ble into masses, I have not been able to trace the distinct arrangement of cells, mentioned by Morgagni and Boyer. Weidmann mentions, that in one case the matter of steatom was a sort of liquefied fat, and in another firm and dense, and not divided into lobes or cells. The other forms of encysted tumours, distin guished by the names of atheroma, (a0v)m.toc, pulticula,ab aOcceoc, pultis gcnus,) and meliceris (1cowtne‘c,mel and cera, honey wax,) are to be viewed rather as varieties of the steatom than as generically different. The substance con tained may differ in consistence, but is nearly the same in essential qualities.
8. lliclanosis.—The adipose membrane is a frequent seat of this singular deposition. The black or melanose matter is found in the sub cutaneous adipose membrane, and the subja cent cellular tissue of the chest and belly ; it is not uncommon in the fat of the orbit ; it is very commonly seen in the adipose cushion on the forepart of the vertebral column, on that sur rounding the kidneys, and in the fat of the anus and rectum ; it is found in the anterior and posterior mediastinum ; and it is found be tween the folds of the mesentery, of the meso colon, and of the omentum. It is also found
in the substance of the marrow of bones ; and, perhaps, in most cases in which the osseous system appears to be stained with the melanose deposite, the dark matter may be traced to the medullary particles, the situation of which it is found accurately to occupy.
In all these situations it appears in various degrees of perfection, and in different forms. It may be disseminated in black or inky spots, through the adipose membrane; it may be ac cumulated in spherical or spheroidal masses of various size and shape; or it may be found in the ..form of brown or ebon-coloured fluid or semifluid, enclosed in a cyst formed of the contiguous tissue, more or less.condensed.
The melanose matter is entirely destitute of organization, and is to be regarded as the result of a peculiar secretion. No vessels have been traced into it; and when bodies affected with this deposite are minutely injected, the vessels can be traced no farther than the enveloping cyst. (Breschet.) It is also to be noticed that it is never deposited exactly in the site of orga nic fibres, but always between them, and very generally in the precise situation of the adipose particles. These several circumstances show that the melanose disease consists not in a de generation or conversion into another substance, but in the deposition of a new form of matter in the manner of a secretion.
In what form the melanose substance is first deposited we have few accurate facts to enable us to form a judgment. Laennec is of opinion that it is first deposited in a solid form, and afterwards becomes fluid. The former he con siders the stage of crudity, the latter that of softening (ramollisement.) Several facts, how ever, would lead to the conclusion, that when first deposited it was fluid, and afterwards ac quired consistence. Thus in several dissec tions performed by Drs. Cullen and Carswell,* the matter of the small tumours, which are supposed to be of short duration, were found to be softest, and sometimes as fluid as cream. In like manlier, in a case recorded by M. Chomel, in which the disease was found in the liver in the shape of large cysts, the melanose matter was more fluid in the centre than in the circumference of the cysts. Upon the whole, if the melanose deposite be, as is supposed, an inorganic secretion, the idea of its being poured forth from the vessels at first in a fluid or semi fluid state is most probable, and most consis tent with the usual phenomena and laws of animal processes.