It is certainly difficult to reconcile the mind to the idea that the process of irritation or of inflammation can, under any circumstance, excite the development of an animal possess ing-, to a certain extent an independent ex istence, but this is not more difficult than to conceive that molecules of a plastic living substance may form organic membranes, and yet this is demonstrable.
This has been clearly shewn in the article ADHESION; in fact, the more we study the phenomena of organisation, the more we are impelled to admit a proper vitality in certain products of living bodies. The analogy which exists between false membranes and hydatid sacs appears to be especially calculated to elucidate this subject. But whilst the false membrane remains in vital communication with the individual, the acephalocystic false mem brane is detached and enjoys an independent life ; the false membrane acquires a vitality rivalling that, of normal tissues.
We believe, therefore, that a cyst may be developed, which, as far as general appearances are concerned, shall be analogous to the ace phalocysts, wanting, however, the one great attribute, independent existence, and having a vascular communication with the tissue upon which it is developed : are not those cysts which are often seen upon the cortical sub stance of the kidney, and upon other organs; of this class or character ? Dr. Hodgkin* has inferred that those cysts which are so often found on the surface of the kidneys owe their existence to the obstruction of an excretory canal ; others have believed that this fact was demonstrated, because it was said that their contents had the odour of urine. Without denying this position, I may state that the smell of serum and that of limpid urine are not very dissimilar. If they were a consequence of the obstruction of an urinary duct, it is evident, from the size they some times attain, that secretion has proceeded after the obstruction has been developed ; why then does it not go further ? why do they not attain considerable magnitude? In the earlier periods of their existence the organisation of these bodies is simple, but in their progress they may experience many mo difications. Their internal and external sur faces are essentially different; the internal is usually smooth and polished like serous niem branes ; sometimes it is soft, flocculent, and easily detached : the external is in contact with cellular tissue, and partakes more or less of its character, but frequently it acquires a density which distinctly separates it from the surround ing tissue. There is scarcely any form of trans
formation which may not occur in these organs. The internal surface occasionally acquires a very complicated organisation ; it may be co vered with hair proceeding from follicles de veloped in its parietes, and it may present other anomalies. The external surface may acquire a very considerable density, and may present something like a fibrous appearance, but upon further investigation we find that it does not possess any fibre, neither does its texture offer any linear or radiated arrange ment. When once organised, the tunic which constitutes the cyst enjoys all the attributes of living tissues, and is susceptible of similar morbid modifications. It may become in flamed, it may degenerate into a cartilaginous state,--may become incrusted with phosphate of lime, converted into erectile tissue,—may become scirrhous, and so on ; and the ex halation or secretion may be so changed that cysts of similar origin may contain the most dissimilar products.
DEATIL—(Lat. mors ; Gr. ObaToc; Germ. Tod ; Fr. mort ; Ital. morte.) This word has acquired a variety of meanings, whichit will be proper to enumerate, before explaining the sense to be adopted in the following article.—Death sometimes expresses the time when an organic body loses the characters which distinguished it while living ; in which signification it is the opposite, not of life, but of birth, or the period when life began ; this period being dated in the animal either from the time when it left its ovum or its parent, or from the very moment of con ception ; and in the vegetable,- either from its emergence above the earth, or from the first impulse of germination. In another acceptation, Death is that altered condition of an organic body in which it is no longer the subject of certain processes which con stituted its life. Thirdly, it may signify that series of changes which immediately precede the cessation of life ;—in this meaning, death is the act or process of dying. Lastly, in the human subject, the word is employed to express the separation of the soul from the body. It will be our object not so much to follow out these several significations, which would lead into a very wide if not a vague discussion, as to consider the precise nature of that condition of the animal body to which the term Death in its physiological import is applicable, and to enquire by what signs that state may be known to be either impending, or actually present.