This occurs occasionally, as we have seen, in acute enlargements of the organ. But traumatic rupture is much more frequent This is effected by blows or falls on the abdomen, and also by injuries to the chest by which the lower ribs are forced against the organ. There may be considerable rupture without any external marks of injury. It is important to remember that the enlarged and hard spleen is more liable to rupture than the normal one, both on account of its more brittle character and its size. This is important in a medico-legal aspect, especially in malarious districts. The rupture may lead to fatal haemorrhage, but as the lesion is often associated with other injuries, the bleeding only plays a part in the result. On the other hand, the haemorrhage may be slight, and the wound may heal and leave a cicatrix.
Of these by far the most important is Amyloid disease. It has already been mentioned that the spleen is more frequently the seat of this disease than any other organ, and that it appears in a majority of cases to be the organ primarily affected. There are two forms of amyloid disease, called respectively the Sago form and the Diffuse form or waxy spleen, to which a third or combined form may be added. In the first the Malpighian bodies are mainly engaged; in the second the pulp. We are entirely ignorant of the conditions which induce these differences in the situation of the degeneration, but it may be said that the sago spleen is peculiarly that which occurs in phthisis pulmonalis, while the waxy form occurs in syphilis.
The Sago spleen is a moderately enlarged organ. On section we observe on the cut surface, instead of the normal small Malpighian bodies, transparent glancing areas which have been very aptly compared to grains of boiled sago. These are dotted over the surface in great profusion. On applying a solution of iodine the affected areas stand out as brown spots, which become of a deeper colour on adding dilute sulphuric acid. Microscopic sections (see Fig. 263) show transparent hyaline areas of circular outline and larger or smaller size, often so large that they are continuous with one another at the peripheries. These areas represent Malpighian bodies, whose normal structure, when the disease is advanced, is entirely replaced by a nearly homogeneous transparent material. In the early stages, however, the addition of methyl-violet or iodine brings out a beautiful network in the Malpighian body, and it is obvious that the reticulum is first attacked. The lymphoid corpuscles disappear as such, probably by atrophy on account of the pressure of the affected reticulum. The arteries whose lymphoid bodies are thus affected are often themselves degenerated, but they may remain unaffected. In advanced stages of the disease the enormous enlargement of the Malpighian bodies causes atrophy of the pulp, and we may have the spleen presenting little beyond large round, sago-like bodies. The pulp may, however, itself take part in the amyloid disease at the periphery of the Malpighian bodies.
Fig. 263. - Section of a sago spleen. The enlarged and translucent Malpighian bodies are seen. In the middle an artery with amyloid walls, x 20.
The diffuse amyloid spleen presents much greater enlargement than the sago form. It is in the highest degree hard and heavy, and the edges rounded. On section the tissue seems homogeneous and inelastic, and of a dark translucent appearance, which has been compared to that of wax or bacon, hence the names Waxy and Lardaceous spleen, which are most appropriately applied to this form. The degeneration affects the greater part of the spleen, but there may be islands of normal pulp visible. The Malpighian bodies are hardly visible, and the cut surface has;i smooth uniform appearance. The application of iodine produces a general deep brown coloration of the tissue. Under the microscope (as shown in Fig. 264) it is seen that the walls of the sinuses of the pulp are involved. On account of the greater density of the amyloid material the honeycomb structure of the pulp is often brought out in a much more striking manner than is possible in a normal spleen. This is more marked if the sections be stained with methyl-violet, the trabecular assuming a bright colour and becoming very manifest. In the later stages the appearance is more uniform, but indications of the trabecular arrangement may still be visible. By the enlargement of the pulp the Malpighian bodies arc greatly atrophied, but they may show traces of amyloid disease. In this form the walls of.the arteries and veins are usually amyloid.
Tuberculosis does not occur in the spleen as a primary disease, but in acute general tuberculosis we frequently find tubercles in great abundance. The tubercles are usually seated in the neighbourhood of arteries, and are often difficult to distinguish from the lymphoid Malpighian bodies which have a similar seat. The existence of the giant-celled structure and the tendency to caseous degeneration will assist in distinguishing them. Occasionally we meet with large caseous masses in the spleen, which may reach the size of walnuts. These occur mostly in children who are the subjects of tuberculous disease of the lymphatic glands of the abdomen. The general distribution of the nodules suggests that the infective material has been carried by the blood, and in some cases there m;:y have been a rupture of a softened gland into the splenic artery. Syphilitic gummata are rare in the spleen, and have been met with chiefly in congenital cases. In Hodgkin's disease the spleen is generally the seat of new-formations, and there is usually great enlargement of the organ (see p. 326).
Fig. 204. - Diffuse amyloid spleen. The swollen and translucent tissue of the pulp (a) is shown, x 400. (After Kyber).
Tumours proper are equally rare, but cases of Fibroma, Sarcoma, and one case of a pulsating Cavernous angioma have been observed. Cysts, which may be single or multilocular, are of occasional occurrence in the spleen. Small cysts with clear contents are occasionally met with in considerable numbers towards the surface of the organ, and probably arise by inclusion of portions of the peritoneal endothelium. Sarcomas occur secondarily in the spleen with greater frequency than any primary tumour, and this is especially true of melanotic sarcomas, which may possibly originate in the spleen. Secondary cancers are very rare even in cases where a generalization of the cancer has occurred by the blood. Extension may occur from the peritoneal surface into the spleen in cases where, from cancer of the stomach or otherwise, the peritoneum is engaged.
Parasites are very unusual in the spleen. The Echinococcus is the most common, forming hydatid cysts, sometimes of large size.
Heinrich, Die Krankh. der Milz; Birch-Hirschfeld, Arch. d. Heilk., xiii., 389, and Lehrb.; Rolleston, in Allbutt's System of medicine, vol. iv.; Friedreich, Acute splenic tumour, in Volkmann's Samml., Syd. Soc. transl., 2nd series, 1877; Mosler, Zeimssen's Encycl., 1878, viii.; Prenner, Gewicht der Milz bei verschied. Krankh., 1885; Albrecht (accessory spleens), Ziegler's Beitriige, xx.; Heusinger, Entziind. d. Milz, 1823; Moxon, (Abscess in ulcerative endocarditis) Path, trans., xix., 198; Bright, (Chronic splenic tumour) Guy's Hosp. liep., iii.; Kyber, (Amyloid disease) Virch. Arch., lxxxi., 1880; Wichmann, Ziegler's Beitrage, xiii., 1893; Langhans, (Cavernous turn.) Virch. Arch., lxxv., 373; Spill-mann, (Cystic haematoma) Arch. d. Phys., 1876, 419; Renggli, Ueber multiple Cysten der Milz, Zurich, 1894; Thornton, (Multilocular cyst) Path, trans., xxxv., 1884; Weichselbaum, (Sarcoma) Virch. Arch., lxxxv., 562; Baumgarten, (Syphilis) Virch. Arch., xcviii.; Bastian, (Hydatid cyst) Path, trans., xviii., 257.