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the veins give rise to, but they present a different chemical constitution. Their minuteness also and their friability favour their penetration into the smallest vessels in a high degree. Therefore we do not so very unfrequently find the obstructing mass in minute microscopical vessels which are no longer to be followed with the naked eye, and in them it usually extends as far down as a point of division and somewhat beyond. This mass constantly presents a finely granular appearance, and does not consist of the coarse debris that we find in the veins, but of a very fine, yet at the same time dense, granular matter; chemically, it possesses the extremely convenient quality for examination of being remarkably resistent to the ordinary tests, and thus readily distinguished from other matters. This is capillary embolia properly so called, one of the
Fig. 74—75. Capillary embolia in the tufts (penicillin) of the splenic artery after endocarditis (Cf. Gesammelte Abhandlungcn zur wiss. Medicin, 1850, p. 716). 74. Vessels of a tuft magnified 10 times, in order to shew the position of the occluding emboli in the arterial district. 75. An artery filled a little before its division, and in the branches into which it next divides, with fragments of the finely granular embolic mass (Cf. Fig. 73, <:). 300 diameters.
most important forms of metastasis, which frequently gives rise to minute deposits in the kidney, the spleen, and the substance of the heart itself; in certain cases occasions sudden occlusions in the vessels of the eye or brain, and according to circumstances produces metastatic deposits or sudden functional disturbances (amaurosis, apoplexy). Here too one can clearly convince oneself that in recent cases the wall of the vessel is quite unaltered at the seat of the affection; nay here indeed the doctrine of phlebitis would no longer suffice, since these are not vessels which possess vasa vasorum, and concerning which it might be assumed that a secretion proceeded from the wall inwards. In these cases it is impossible to regard the occluding mass in any other light than as one primarily existing in the vessel, and in no wise dependent upon the condition of its wall.
Perhaps this description has convinced you, gentlemen, that two essential errors have existed in the doctrine of pyaemia; the one, that people thought they had found puscorpuscles in the blood, when only colourless blood-corpuscles were really present; the second, that they thought they had found pus in vessels in which nothing more than the products of the softening of fibrine existed. Yet we have ascertained that this last class of cases certainly furnishes the most important source of genuine metastatic deposits. But in my opinion, the history of the processes which have been called pyaemia is not confined to these conditions. When the process runs its course free from all complication, so that from the original seat of the disease (thrombosis in a vein, endocarditis, &c.) only solid masses in an undecomposed state are detached and cause obstructions, the real process is in many cases brought to notice only in consequence of the metastasis. There are cases which run their course so latently that all the earlier stages of the affection are entirely overlooked, and that the first rigors which declare themselves
METASTASES DUE TO INFECTANT MATTERS. SPLEEN. 211
announce that the development of the metastatic processes has already set in. Usually, however, another condition must be taken into consideration, which is not directly accessible either to the coarser or more delicate modes of anatomical investigation; I mean certain fluids, which in themselves bear no immediate and necessary relation to pus as such, but manifestly differ very much from one another in their nature and origin.
Whilst I was engaged in the consideration of the changes which lymph undergoes, I pointed out to you (p. 186), that fluids which were taken up by lymphatic vessels were not only freed in the filters of the lymphatic glands from corpuscular elements, but were also in part attracted and retained by the substance of the glands, so as to display some activity within them. Similar effects appear to take place also elsewhere than in the glands. Where the reabsorption was primarily effected by the veins, this must, of course, always be the case. There is namely a series of peculiar phenomena which pervade all infectious processes as a constant element. These are on the one hand the changes which the lymphatic and lymphoid glands may undergo not so much at the seat of the primary affection as rather in the body generally, and on the other hand the changes which the secreting organs offer, through which the matters were to be excreted.
It was for some time believed that tumefaction of the spleen was characteristic of typhoid fever, inasmuch as it formed a parallel to the swellings of the mesenteric glands occurring in that disease. But more accurate observation has shewn that a great number of feverish conditions which follow a more or less typhoid course, and affect the nervous system in such a manner that a state of depression is brought about in its most important central organs, set in with swelling of the spleen. The spleen is a remarkably sensitive organ, which swells not only in intermittent and typhoid fever, but also in most other processes in which noxious, infectant matters have been freely taken up into the blood. No doubt the spleen must always be considered in its near relationship to the lymphatic system, but its diseases in addition usually bear a very direct relation to analogous diseases of the important glands in its vicinity, especially the liver and the kidneys. In most cases of infection do these three organs exhibit corresponding enlargements connected with real changes in their interior; but since these changes do not, even on microscopical examination, apparently present anything remarkable, the attention of the observer is chiefly attracted by the result which is obvious to the naked eye, namely, the great swelling. On careful comparison, however, a good deal is discovered, so that we can affirm with certainty that the gland-cells quickly become changed, and that disturbances early shew themselves in the elements by means of which the secretion is to be accomplished. I shall revert to this subject hereafter. Allow me now, in elucidation of these conditions, in the first place to advert to one or two more obvious examples which are accessible to direct observation.
We know that when any one takes salts of silver, they penetrate into the different tissues of his body; and if we do not employ them in a really corrosive and destructive manner, the silver penetrates into the elements of the tissues in a state of combination, the nature of which has not yet been satisfactorily made out, and, when it has been made use of long enough, produces a change of colour at the point of application. A patient who had in Dr. Von Graefe's out-patient room on the 10 th November received a solution of nitrate of silver as a lotion, very conscientiously employed the remedy up to the present time (17th March); the result of which was that his conjunctiva assumed an intensely brown, nearly black appearance.
DEPOSITION OT SILVER IN THE TISSUES. GOUT. 213
The examination of a piece cut out of it shewed that silver had been taken up into the parenchyma, and indeed in such a manner that the whole of the connective tissue had a slightly yellowish brown hue upon the surface, whilst in the deeper parts the deposition had only taken place in the fine elastic fibres of the connective tissue, the intervening parts, the proper basis-substance, being perfectly free. But deposits of an entirely similar nature take place also in more remote organs. Our collection contains a very rare preparation from the kidneys of a person who on account of epilepsy had long taken nitrate of silver internally. In it may be seen in the Malpighian bodies, in which the real secretion takes place, a blackish blue colouring of the whole of the membrane of the coils of the vessels, limited to this part in the cortex, and appearing again, in a similar, though less marked form, only in the intertubular stroma of the medullary substance. In the whole kidney, therefore, besides the parts which constitute the real seat of their secretion, those only are altered which correspond to the ultimate system of capillaries in the medullary substance. Of the well-known discoloration of the skin by silver I need not speak here.
Another instance is afforded us by gout. If we examine the concretions (tophi) in the joints of a gouty person, we find they are composed of very delicate, needle-shaped, crystalline deposits of all possible sizes, and consisting of urate of soda, with at most here and there a pus- or bloodcorpuscle lying between them. We have here therefore also, as when silver has been employed, to deal with a material substance which is usually excreted by the kidneys, and that indeed not rarely in such large quantities, that deposits form even within the kidney itself and large crystals of urate of soda accumulate, especially in the uriniferous tubules of the medullary portion, so as sometimes to lead even to an occlusion of the tubules. If, however, this