A system of practical medicine. By American authors. Vol. 1

by Unknown

²⁰ Virchow's Archiv, 1875, lxxii. 85.

Thrombi are frequently stratified, in consequence of the successive deposition of new layers of blood-corpuscles and fibrin upon a pre-existing thrombus. Circulating blood is therefore necessary for the stratification, and such thrombi are likely to be mixed in color. Unstratified thrombi are usually white or red, the former largely composed of agglomerated white blood-corpuscles so moulded and situated as to prevent a stagnation of blood in their vicinity, while the red thrombus is rarely stratified, since its formation demands a stoppage of the blood-current. Stratification is intimately connected with the enlargement or growth of the thrombus, which takes place from the surface exposed to the flowing blood, and which is greater or less according to the seat of the thrombus.

Thrombi are usually divided into those from compression, dilatation, traumatism, and marasmus; in all of which groups an abnormal condition of the endothelium is to be met with.

Thrombi from compression are frequently formed in veins, in the vicinity of growing tumors. Their presence is most constant when the vein is compressed between a resistant surface, especially bone, and the tumor. A compression of the smaller blood-vessels within an organ, as the liver or kidney, may take place in consequence of chronic interstitial inflammation, or the growth of cancerous or other malignant tumors in such organs. The production of this form of thrombus is sought for in the treatment of certain aneurisms by direct pressure, the resulting stagnation of blood being followed by a coagulation within the aneurismal sac.

Thrombi from dilatation are met with both in dilated arteries and veins. In aneurism and varix a slowing of the blood-current is present, and the intima of the diseased region is frequently in such an abnormal condition that a clotting of the blood readily takes place. The shape and situation of the dilatation are of importance in promoting the formation of the thrombus; the more pedunculate and the more voluminous the sac the more certain is the thrombosis.

Traumatic thrombi result from a direct injury to the vessel. This may be mechanical, as in the application of ligatures for the obliteration of vessels, the tearing of the veins during childbirth, and the infliction of wounds of every variety. The injury may likewise be chemical, from the action of caustics; somewhat analogous to which, are the effects of heat and cold. Allied to the traumatic thrombi are those which arise from acute inflammation of the intima extending from wounds or inflammatory processes in the vicinity of blood-vessels.

Marantic thrombi are those whose origin is attributable to that enfeebled condition of the body known as marasmus. This represents a weakening of the several functions, especially the circulation, respiration, and locomotion. Such may take place in disease or old age; and it is important to bear in mind those diseases in which marasmus is likely to arise, as thrombosis often proves a complication of such affections. Protracted fevers, as typhus and typhoid, puerperal diseases, the disturbances following surgical operations, chronic wasting diseases, as the tuberculous and scrofulous affections, are all likely to be accompanied by thrombosis. Stagnation of the blood, as well as alterations of the intima, is an important local condition in this variety of thrombosis, which is usually valvular or parietal at the outset, and may be both arterial and venous. Such thrombi are likely to become continued and to serve as a frequent source of embolism.

Thrombi are also divided into primitive, or autochthonous, and secondary varieties. The primitive thrombus is one which owes its local origin to conditions existing at the place of its formation and attachment. The secondary variety demands for its existence a primitive thrombus, whose place of development is remote in time and seat, and from which a part has been transferred to serve as the nucleus for the secondary formation.

The continued thrombus is often confounded with the secondary variety. Continuance is rather a quality of all thrombi, and is essentially growth, whether by lamellation or agglomeration. Such continued thrombi are extended in the course of the circulation, usually by a conical end, which is pointed toward the heart in the case of venous thrombi, but away from this organ when the thrombi are arterial.

Parietal and obstructing thrombi form another subdivision. The former arise from a limited part of the wall of the heart or blood-vessel, and project into its cavity. They are always in contact with flowing blood, and are white or mixed in color and primitive. They may attain a considerable size, and may eventually become obstructing thrombi. The latter are so called when they are of sufficient size to cause a considerable or total obstruction to the current of blood. In the last case the vascular canal is wholly filled by the thrombus. The shape of the older parietal forms is usually globular or pedunculate, owing to the growth in all directions except at the place of attachment; the obstructing thrombi are elongated.