By the irritative character of the thrombi themselves, they excite inflammatory action in the adjoining tissues; in this way are produced multiple abscesses. Therefore, we find in persons who die under such conditions, abscesses in the brain, heart, lungs, kidneys and intestines; further we may find purulent inflammation and abscesses in the connective tissues.
It is now necessary to explain the nature and composition of both the thrombus and embolus, and how, through their mechanical agency, the process of embalming may become seriously impaired, if not altogether arrested. A thrombus is a clot, composed principally of the fibrine of the blood, formed during life in the cavities of the heart, the arteries, the veins, or the capillaries.
An embolus is a solid body, usually a portion of a thrombus, carried by the blood current into some artery or capillary, and becomes fixed there. A thrombus may entirely fill the cavity of a vessel, or it may only form a layer on its wall, or it may project from a smaller vessel into a larger one.
An embolus may completely or only partly plug up a vessel; it may remain alone or a thrombus may be formed around it.
A thrombus may merely become harder and whiter in time, or it may become organized, or it may degenerate, soften, and change into a mass of puriform fluid and gangrenous looking fibrine, or it may calcify.
The production of thrombi is due to various causes.
(1.) Spontaneous thrombi are produced by any cause which seriously weakens the whole system, as old age and chronic exhaustive diseases. They are usually formed in the veins of the lower limbs and pelvis, and in the sinuses of the dura mater.
(2.) Compression of the vessels by ligatures, tumors, dislocated bones, and inflammatory exudation. Pneumonia may produce thrombosis of the pulmonary veins. Phthisis may produce thrombosis of the pulmonary arteries.
(3.) Thrombi may form into capillaries or small veins, and increase until they project into larger veins.
(4.) It may also form when there is inflammation, especially of a gangrenous and suppurative nature, in the parts around a vessel.