An introduction to pathology and morbid anatomy / by T. Henry Green.

Date:
1878
    regains its former appearance. If tTie application of the iodine be followed by the cautious addition of sulphuric acid, a blackish-blue or violet tint is produced. This latter reaction, however, is not easily obtained, consi- derable nicety being required in the application of the reagents. The following is the method for obtaining it, recommended by Professor Virchow:—A dilute aqueous solution of iodine must be allowed to soak well into the tissue, the excess must be poured off, and a single drop of concentrated sulphuric acid gradually added, when a blue or violet colour will be produced, either at once or after some time. In the hands of English pathologists this latter reaction has certainly met with bat little success; and if the colour be obtained, it is by no means satis- factory, and more neai'ly resembles a black than the blue which has been described. Fortunately, however, the reaction with iodine alone is perfectly characteristic, and the attempt to obtain the blue by the subsequent addition of sulphuric acid is therefore quite unnecessary. If the change is at all advanced, the reddish-brown colour will be produced by merely pouring the aqueous solution of iodine over the cut surface of the organ; but in slighter degrees of the affection, thin sections must be made with a Valentin's knife, and well washed with water to remove the blood, before the coloration with iodine can be ob- tained. Upon considering the above reactions, it will be seen that they resemble, in some respects, those exhibited by some well-known oi'ganic substances. Cellulose—the substance which forms the external membrane of vege- table cells—yields a blue when treated with iodine and sulphuric acid, and so far resembles the amyloid mate- rial ; but it differs in not being coloured by iodine alone. The same is true of cholesterine; this also gives a reddish- brown with sulphuric acid, but is not altered by iodine. To starch, the resemblance is not so marked as to the two preceding substances; with this, iodine produces a blue colour without the addition of the acid.
    The amyloid substance almost invariably makes its appearance first in the small arteries and capillaries, and subsequently extends from them to the surrounding tis- sues. The cells of the intima and of the muscular coat are the first to become infiltrated, then the remaining structures of the artery. When the vessels have become infiltrated, the amyloid matter extends to the immediately surrounding parts; it invades both the cells and the intercellular substance, and may gradually extend until the whole organ is completely impregnated. The changes produced in the tissues by this infiltration are very characteristic. The cells as they become filled with the new material gradually increase in size ; they lose any irregularities in their contour, and become rounder and more regular in shape; their nuclei dis- appear, and the whole cell is converted into a structure- less homogeneous body, which has a peculiar translucent glistening appearance. (Fig. 17, a.) If the cells are in Fig. 17. Liver Cells infiltrated with the Amyloid Substance, a. Single cells, 6. Cells which have coalesced X 300. (Rindfleisch.) close contact many of them may coalesce, and their dis- tinctive boundaries thus become obliterated. (Fig. 17, h.) The intercellular substance in the same way acquires a homogeneous glistening appearance. The walls of the small arteries—in which, as already stated, the change commences—become considerably thickened, the cells of the muscular coat enlarge and ultimately coalesce, the calibre of the vessel becomes diminished, and the cir-
    culation througli it is consequently impeded. (See Fig. 19.) Organs in which this change is at all advanced, present features so characteristic that its nature can be readily recognised by the naked eye. They are usually consider- ably increased in size ; their absolute weight is increased, and also their specific gravity; their surface is smooth, and the capsule tense and stretched; their consistence is firm and somewhat elastic. On section they exhibit a peculiar homogeneous, glistening, translucent appearance, somewhat resembling wax or glue. Owing to the dimi- nished calibre of their blood-vessels and to the pressure exercised by the new material, they contain but little blood, and hence are always pale in colour. The change may involve the whole organ, or it may be hmited to certain portions. In the spleen, for example, it is fre- quently limited to the Malpighian corpuscles ; and in the liver to the cells in the more immediate vicinity of the hepatic artery. Although the above characters are often sufficiently marked, they should always be confirmed by the applica- tion of iodine to the cut surface of the organ. In shghter degrees of the affection—when the physical characters are but Little altered—the application of this reagent becomes necessary in order to discover the presence of the new substance. In these cases, merely pouring the solution over the organ will often fail to produce the characteristic staining ; and it will be necessary to make thin sections with a Valentin's knife, and wash them thoroughly with water to remove the blood, before the reaction can be obtained. In the earhest stages of the change the use of the microscope may be necessary for its recognition. The effect of amyloid degeneration is to imjDair or even to completely destroy the nutrition and function of those organs which are affected by it. This is owing to two causes—the obstruction offered to the circulation and the
    7a direct influence of the new material upon the parenchyma of the organ. The obstruction to the circulation, which results partly from the diminution in the' calibre of the small ai-teries, and partly from the general pressure exercised by the infiltrated substance, causes an insuffi- ciency in the supply of arterial blood. As a consequence of this, secondary atrophic changes are induced in various parts ; the cells may atrophy and undergo fatty meta- morphosis, which indeed is fi'equently associated with the amyloid change. The vitaUty of the cellular elements is still further impaired by their infilti-ation with the new material, and thus all manifestation of their functions may ultimately cease. As this form of degeneration is almost invariably secondary to some grave constitutional state, it can rarely be looked upon as in itself a cause of death, although it may materially hasten, and even determine, the fatal termination. Having thus described the nature of the amyloid sub- stance, and the way in which it makes its appearance in the several tissues of an organ, it remains to consider the source from which it is derived. The disease, as already stated, appears to be an infiltration, and to consist in the deposition of a new material from the blood in the various tissues and organs. The existence, however, of any albu- minoid substance in the blood which resembles amyloid in its reaction with iodine, has never been made out, even in the most marked cases of the disease. This fact must therefore negative the supposition that it is a simple infiltration. If the new material be derived from the blood at all, it must undergo some chemical change subsequently to its deposition in the tissues. Dr. Dickin- son considers that it is dealkalised fibrin, which is depo- sited in consequence of the loss of the alkali which it normally contains. This loss of alkali he attributes to the chronic suppuration which usually precedes the disease, pus containing large quantities of potassium and
    sodium salts. He coasequently terras the disease " dejju- rative infiltration.'"* Whether this be so or no, it is probable that some abnormal condition of the blood is the cause of the disease, and that the change itself consists in the retention and coagulation in the tissues of some albuminoid substance which is derived from, the nutritive fluids. The way in which the several tissues of an organ are affected, the change almost invariably com- mencing in the small nutrient blood-vessels, and extending from them to the surrounding parts ; the general charac- ter of the affection, several organs being simultaneously involved; together with the fact that it is almost in- variably secondary to chronic suppurative diseases or to syphiUs—point to some alteration in the comijosition of the blood as the cause of the degeneration. AMYLOID DEGENERATION OF THE LIVER. The liver is one of the most frequent seats of the amyloid change, and here, as in other j^arts, it probably commences in the small nutrient blood-vessels, although the alterations are much the most marked in the hepatic cells. The minute branches of the hepatic artery are first affected, and from these the infiltration gradually extends to the hepatic cells immediately adjacent, until ultimately the whole organ may become involved. If a liver be examined in the earlier stages of the affec- tion, and the iodine solution applied to thin washed sec- tions of the organ, it will be found that the characteristic staining is limited to certain portions of the lobules—viz. to those which are situated between their external and central parts. This intermediate portion corresponds with the distribution of the hepatic artery, and the rami- fications of this vessel together with the hepatic cells situated in their vicinity are the first to become affected. (Fig. 18). As the change advances the whole lobule may • "Modico-Cliu-iirgical Transactions," vol. 1.