Amyloid Metamorphosis is a degeneration of the connective tissues into an abnormal substance giving an amyloid reaction. The origin of this material is obscure. It may be formed in loco, but more probably is brought to the tissue from some other part of the body. It does not exist as much in the blood, but is very probably derived from substances contained in that fluid. Some believe that the leukocytes, others that the erythrocytes, are the cells from which it is derived.

It is frequently called waxy, lardaceous, or "bacony" disease; is found in the intercellular portions of the connective tissues and not in secreting cells.

It is found as a result of long-continued suppuration and ulceration, such as occur in diseases of the bone, chronic tuberculosis, syphilis, leukemia, and dysentery.

The organs most commonly affected are the spleen, liver and kidney, the larger blood-vessels, the mucous membrane of the intestines, the lymph-nodes, and the heart.

The involved organs are generally pale, larger, firmer, and heavier than normal, and with rounded edges. The cut surface is smooth, glistening, and transparent, either diffuse or localized. The usual sites of the degeneration are the walls of the capillaries, in the intima and media, the adventitia being rarely affected.

Fig. 10. - Amyloid Degeneration of the Liver. X 98 (Dürck).

1, Central vein. Portal capillaries surrounded by homogeneous masses and bands; the epithelial lining distinct. Columns of liver cells compressed to narrow, atrophic strips.

In the kidney the capillaries of the glomeruli are first attacked, converting the bodies into waxy, homogeneous masses; finally the connective tissue may be involved.

In the liver the amyloid substance is found between the periportal connective tissue and the central vein, in the intermediate zone which is supplied by arterioles and capillaries of the hepatic artery. In the spleen it may give rise to the "sago spleen," a condition which is brought about by the formation of amyloid material in the Malpighian bodies. Later on, the organ may become very extensively involved. In some cases the vessels in the trabecular of the organ may be the seat of the metamorphosis.

When amyloid material has been once deposited it is practically never removed - It is insoluble in water, alcohol, ether, dilute acids, alkalis, etc. Resists peptic digestion and withstands decomposition for a long time. Unless special staining methods are employed, it frequently cannot be distinguished from hyaline degeneration.

When the affected tissue is placed in Lugol's solution (iodin I, potassium iodid 2, water 100) the amyloid substance becomes a mahogany brown. If stained in 5 per cent, aqueous gentian-violet the amyloid will appear pink; the normal tissues, blue.

If after staining in iodin, weak sulphuric acid (5 to 10 per cent.) is added, the amyloid will turn blue.

Corpora Amylacea

Corpora Amylacea, or amyloid bodies, are found in the prostate gland, in lymphatic nodes, and in the central nervous system. They are concentrically striated like a starch granule, and although in their reaction they may resemble starch and amyloid, they are probably neither.