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offer even the slightest resemblance in its more intimate structure to pus. This was so far tranquillizing, as there is no observation as yet on record of the death of any patient from pyaemia who had sacs of this description even in pretty considerable number, but it ought to have struck those who are so much inclined to establish a connection between peripheral thromboses, which are however just the same thing, and pyaemia.

For the question naturally arises how far particular disturbances that can be designated by the name of pyaemia may, in consequence of the softening of the thrombi, be evoked in the body. To this in the first place we may answer that secondary disturbances certainly are very frequently occasioned, but not so much by the immediate introduction of the softened masses as fast as they become liquid into the blood, as by the detachment of larger or smaller fragments from the end of the softening thrombus which are carried along by the current of blood and driven into remote vessels. This gives rise to the very frequent process upon which I have bestowed the name of Embolia.

This is an occurrence which we can here only briefly touch upon. In the peripheral veins the danger proceeds chiefly from the small branches. By no means rarely do these become quite filled with masses of coagulum. As long however as the thrombus is confined to the branch itself, so long the body is not exposed to any particular danger; the worst that can happen is that, in consequence of a peri- or meso-phlebitis,1 an abscess may form and open externally. Only the greater number of the thrombi in the small branches do not content themselves with advancing up to the level of the main trunk, but pretty constantly new masses of coagulum deposit themselves from the blood upon the end of the thrombus layer after layer, the thrombus is prolonged beyond the mouth of the branch into the

1 See the Author's ' Gesarameltc Abhandl.' p. 484.

EMBOLIA. PROLONGED THEOMBI AND THEIEIMPOET. 205

trunk in the direction of the current of the blood, shoots out in the form of a thick cylinder farther and farther, and becomes continually larger and larger. Soon this prolonged thrombus (Fig. 71, t) no longer bears any proportion to the original {autochthonous) thrombus (Fig. 71, c), from which it proceeded. The prolonged thrombus may have the thickness of a thumb, the original one that of a knitting-needle. From a lumbar vein, for example, a plug may extend into the vena cava as thick as the last phalanx of the thumb.

Fig. 71.

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It is these prolonged plugs that constitute the source of real danger; it is in them that ensues the crumbling away which leads to secondary occlusions in remote vessels. They are the parts from which larger or smaller particles are torn away by the blood as it streams by (Fig. 71, f).

Through the vessel originally occluded no blood at all flows; in it the circulation is entirely interrupted; but in the larger trunk through which the blood still continues its course, and into which only at intervals the thrombusplugs project, the stream of blood may detach minute particles, hurry them away with it, and wedge them tightly into the nearest system of arteries or capillaries.

Fig. 71. Autochthonous and prolonged thrombi, c, tf. Smallish, varicose, lateral branches (circumflex veins of the thigh), filled with autochthonous thrombi, which project beyond the orifices into the trunk of the femoral vein. /. Prolonged thrombus produced by concentrically apposed deposits from the blood, t. Prolonged thrombus, as it appears after fragments (emboli) have become detached from it.

Thus we see, that as a rule all the thrombi from the periphery of the body produce secondary obstructions and metastatic deposits in the lungs. I long entertained doubts whether I ought to consider the metastatic inflammations of the lungs one and all as embolical, because it is very difficult to examine the vessels in the small metastatic deposits, but I am continually becoming more and more convinced of the necessity of regarding this mode of origin as the rule. When a considerable number of cases are compared statistically, the result obtained is that every time metastatic deposits occur, thrombosis is also present in certain vessels. Quite recently, for example, we have had a tolerably severe epidemic of puerperal fever, and in this it was found that, however manifold the forms the disease assumed, yet all those cases which were accompanied by metastases in the lungs, were also attended with thrombosis in the region of the pelvis or in the lower extremities, whilst in the inflammations of lymphatic vessels the pulmonary metastases were wanting. Such statistical results carry with them a certain amount of compulsory conviction, even where strict anatomical proof is wanting.

Into the pulmonary artery the introduced fragments of
Fig. 72. thrombus of course penetrate to different

depths according to their size. Usually
a fragment of the kind sticks fast where
a division of the vessel takes place
(Fig. 72, E), because the diverging vessels
are too small to admit it. In the case
of very large fragments even the prin-
cipal trunks of the pulmonary artery
are blocked up, and instantaneous

Fig. 72. Emboh's of the pulmonary artery. P. Moderately large branch of the pulmonary artery. E. The embolus, astride upon the angle (spur—Sporn), formed by the division of the artery, t, f. The capsulating (secondary) thrombus: I, the portion in front of the embolus reaching to the next highest

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DIFFERENT VARIETIES OF METASTATIC DEPOSITS. 207

asphyxia ensues; other fragments again penetrate into the most minute arteries and there give rise to very minute, and sometimes miliary inflammations of the parenchyma. In explanation of these small and often very numerous deposits, I must mention a conjecture which only occurred to me whilst engaged in my more recent observations, but which I do not scruple to declare to be a necessary inference. I believe namely that, when a considerable fragment of a thrombus becomes wedged at a certain point in an artery, it may in its turn crumble away through the onward pressure of the blood, and thus the minute particles to which this crumbling of the larger plug gives rise be conveyed into the small branches into which the vessel breaks up. Thus alone does it seem to me that the fact can be explained, that in the district supplied by an artery of considerable size a number of little deposits of the same sort are often found.

This whole series of cases has nothing whatever to do with the question, whether there is pus in the blood or not. We have in them to deal with bodies of quite a different nature, with fragments of coagula in a more or less altered condition, and according as this alteration has assumed this or that character, the nature of the processes which arise in consequence of the obstruction may also be very different. If, for example, a gangrenous softening has taken place at the original site of the coagulum, the metastatic deposit will also assume a gangrenous character, just as this would be the case if gangrenous matter were inoculated. So, vice versa, it also happens that the secondary disturbances, like those at the spot whence the fragments were detached, run a very favourable course, the embolus like the thrombus becoming converted into pigment and connective tissue, and at the same time growing smaller.

collateral vessel e; f, the portion behind the embolus, in a great measure filling up 1 he diverging branches r, r1, and ultimately terminating in the form of

This group of processes must be separated from those ordinarily occurring in pyaemia all the more, because the same processes are also met with on the other side of the lungs in the regions belonging to the left side of the circulation, where they often run the same course and present the same results, but are still less dependent upon an original phlebitis. Thus, for example, endocarditis by no means seldom forms the starting point of such metastases. Ulceration takes place in one of the valves of the heart, not by means of the formation of pus, but in consequence of an acute or chronic softening; crumbling fragments of the surface of the valve are borne away by the stream of blood and reach with it far distant

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points. The kind of obstruction which these masses produce is altogether similar to that which the thrombi in

Fig. 73. Ulcerative endocarditis affecting the mitral valve, a. The free, smooth surface of the mitral valve, beneath which the connective-tissuc-corpuscles are enlarged and clouded, whilst the intervening tissue is denser than usual. b. A considerable hilly swelling caused by increasing enlargement and cloudiness of the tissue. c. A. swollen part which has already begun to soften and break up. d, d. The tissue at the lower part of the valves which is still but little altered, with numerous corpuscles, the results of proliferation, e, e. The commencement of the enlargement, cloudiness, and proliferation of the corpuscles. 80 diameters.

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