Disposal Of The Infarction

In the case of the haemorrhagic infarction of the lung, if necrosis does not occur there may be complete restoration. The circulation may be resumed by organization and vascularization of the plug in the manner already described under Thrombosis, and the blood being removed from the alveoli, the air re-enters. (For proof of this see under Lung, haemorrhagic Infarction.) In some cases, however, necrosis does occur, so that, if the patient survive, symptoms like those of phthisis develop, and lung tissue has been known to be spit up. As the necrosed lung tissue is disposed of a cicatrix will take its place.

Fig. 32. - Infarction of kidney undergoing absorption. The infarction is white and depressed below the level while the tissue is puckered around it. (After Rayer).

The solid infarctions in the spleen and kidneys, whether red or white, are treated like dead animal matter in any protected situation among the living tissues. They are gradually absorbed (see Fig. 32) and their place is taken by cicatrices, in the midst of which, even at a late date, little pieces of cheesy-looking material may be seen. In the case of red infarctions, the blood-pigment is first dissolved out of the corpuscles, and then partly absorbed and partly deposited in the form of solid granules, the result being that the infarction becomes pale.

The softened brain tissue is also absorbed, and a cicatrix or a cyst takes its place. So is it with the retina, the piece of tissue is lost and absorbed. In the case of the superior mesenteric artery, the slough of the bowel and haemorrhage lead on mostly to a fatal result, but cases do occur in which, after the separation of a slough, an ulcer is left which may ultimately cicatrize.

Special Forms Of Embolism

(1) Malignant tumours not infrequently extend into the blood and form secondary tumours by embolism. (See Metastasis of tumours).

Fig. 33. - Fat in pulmonary vessels in lipiemia producing embolism chiefly of the capillaries. (Saunders and Hamilton).

(2) Fat-Embolism

Oil or fluid fat not infrequently gets into the blood, and it may obstruct the small arteries and capillaries (see Fig. 33). This occurs mostly in consequence of fracture of bones, but also after injuries to the subcutaneous adipose tissue, as in operations, or from rupture of the liver when it contains fat in excess. In these cases the fat finds entrance to the blood by the veins which are ruptured, but there are cases in which apparently it reaches the blood circuitously by the lymphatics; in suppurations occurring in parts rich in fat, such as the uterus after delivery (endometritis), this may occur (Cohnheim). Oil also occurs in the blood in cases of diabetes. (See Lipsemia).

The oil finds its way, carried by the blood, to the right side of the heart and on into the lungs. If small in quantity it obstructs a few capillaries and small arteries, and there is no appreciable effect. But if a considerable number of small arteries near each other be obstructed, or even a large number of capillaries, we may have a condition resembling the haemorrhagic infarction. In some cases the oil may, to some extent, pass through the lung capillaries, and it is then found mostly in the Malpighian tufts of the kidney, one or two loops being here and there filled. There are a few rare cases on record in which extensive embolism has occurred in the smallest vessels of the brain, conjunctiva, skin, muscles, heart, intestines, liver, and kidneys, and has apparently been the cause of death.

The oil may be detected in the capillaries or small arteries in the lung or elsewhere, especially in sections which have been treated with osmic acid. .

(3) Air-Embolism

The admission of a considerable quantity of air into veins near the heart often leads to a fatal result, and some have supposed that embolism in the lungs is the cause. As the pressure in the veins near the heart is very low, and there is even a degree of suction during inspiration, there is great danger in opening such a vein as the jugular. Air admitted at a distance from the heart, as by the uterine veins after delivery, may also cause death (see case referred to by Birch-Hirschfeld). In regard to the cause of death in these cases it is important to notice that a repeated admission of small quantities of air does not produce serious results, whereas a single large admission is rapidly fatal. This hardly looks as if embolism were the cause, and as a matter of fact, the air is found after death mainly churned up with the blood in the right auricle and ventricle, which are usually enormously dilated. It seems that the right ventricle, in contracting, merely squeezes together the elastic air which again expands during the diastole. The force of the heart is thus fruitlessly expended and the blood is not sent into the pulmonary artery. Moreover, the over-distension of the right auricle with air prevents the admission of blood from the venae cavae. Thus the circulation is at a standstill and death results.

(4) Infective Embolism

Hitherto the phenomena of embolism have been referred to on the supposition that the obstructing plug is in itself of an indifferent nature. If this is not so, and especially if the plug contains specific microbes, more particularly those of inflammation (pyogenic), then the results are very different. In some cases the veins are in communication with wounds which are the seat of decomposition, and the-thrombi which form contain pyogenic microbes. If embolism occurs, then each embolus, whether in an artery or capillary, is likely to form a centre of inflammation. Hence arise multiple abscesses, chiefly in the lungs, but also in the kidneys, liver, and elsewhere. A similar infective embolism may occur in consequence of the existence of a focus of infection in the heart. (See Ulcerative Endocarditis).

Literature

Vikchow, as under Thrombosis; Cohnheim, Neue Untersuchungen iiber die embolischen Processe, 1872; Allgemeine Pathologie, 1882, chap. iv.; Cohnheim und Litten, Virch. Arch., lxv. and lxvii.; Kossuchin, Virch. Arch., lxvii.; Recklinghausen (Retrograde Embolism), Virch. Arch., c.; Grawitz, Hrem. Infarkte der Lunge, 1891; Hamilton, Text-book of Path., i. (583, 1889; Fcjinami, Virch. Arch., clii., 61 and 193, 1898; Embolism of superior mesenteric artery - Litten, Virch. Arch., lxiii.; Moyes, Glasgow Med. Jour., 1880 (full account of literature, etc.). Fat-embolism - Zenker, Beitriige, z. norm, und path. Anat. d. Lunge, 1862, p. 31; Wagner, Arch. d. Heilk., 1862, iii., 241; Busch, Virch. Arch., 1866, xxxv., 321; Scriba, Deutsch. Zeitschr. f. Chirurgie, xii., 118; Saunders and Hamilton, Edin. Med. Jour., July, 1879. Air-embolism - Amussat, Introduction de Pair dans les veines, 1839; Panum, Virch. Arch., xxv.; Couty, Etude exper., 1875; Birch-Hirschfeld, Lehrbuch d. path. Anat., 1896, vol. i., p. 36.