— The first change in a thrombus is a shrinking process, during which it becomes denser. Decolorization follows, and it becomes tougher, denser, or even somewhat friable. The subse quent changes vary much.
The thrombus may continue to shrink and dry up until it becomes tough and leathery or even calcified (phleboliths).
Softening may take place either as a re sult of molecular disintegration or more rarely of suppuration. In the former case the thrombus liquefies, forming a milky fluid consisting of an oily and granular detritus, the softening beginning in the centre.
Suppuration occurs occasionally in venous thrombi surrounded by, or lead ing from, inflamed parts, the number of leucocytes in the thrombus becoming in creased either by proliferation or immi gration and the whole melting down into a purulent fluid. The wall of the vein, in these cases, is itself always inflamed, and these softened and broken-down thrombi are a common cause of embolism.
Finally, the thrombus may become or ganized, new tissue growing into it from the vessel-walls and forming a vascular reticulated connective tissue, in the meshes of which are found the remnants of the red blood-globules and fibrin of the clot. Progressive dilatation of the newly formed vessels gradually renders the thrombus cavernous (canalized throm bus), and finally. by their coalescence, the clot finally disappears and the vessel again becomes pervious.
Thrombosis of the crural veins is more common after pelvic operations than is generally recognized. It occurs fre quently in those ea.es in which large tumors of the pelvic organs have been removed. It rarely follows extrapelvic operations. In this series it has been infrequent after infected cases. The and cachexia in consequence of new growths seem to be factors in its causation. Constipation and the use of enemata play a doubtful part in the etiology. Traumatism at the time of the operation should be borne in mind, and deep retractors used with extreme care. infection is undoubtedly of great importance, but its frequency is difficult to decide. This complication often oc to decide. This complication often ()e late in convalescence. Albumin in the urine is more frequent in these cases than in those running. an uninterrupted course. Rest and elevation for the full length of time arc excellent. Schenck (New York Med. Jour.. Sept. G. 1902).
Treatment.—The treatment of throm bosis varies according to the seat of the process, and is mainly prophylactic. Great care should be taken that the thrombus does not give rise to emboli. It is necessary, therefore, to keep the part at rest until organization or absorp tion of the thrombus has taken place.
As a preventive of thrombosis in the veins of the lower extremity after ab dominal operations, raising the foot of the bed after all operations within, or in the region of, the abdomen has been per sonally performed, and thrombosis has hot been observed except in one case, in whom, for some reason or other, the rais ing of the foot of the bed was omitted. Where the heart's action was and the blood-pressure was low, recourse was also had to stimulants, to infusions of salt solution, etc. Care was also taken that the bandages did not compress the saphena or femoral veins. Lennander (Centralb. f. Chin. May 13. '99).
Embolism.—Embolism is the arrest in the arteries or capillaries of some foreign body which has been carried along in the course of the circulation. The term is applied to the foreign body or substance which, being carried in the blood-stream to some other part of the circulatory system, is arrested and forms a plug which occludes the vessel in which it is arrested, and may consist of a de tached fragment of a thrombus, a vegeta tion or vegetations detached from the heart-valves, fragments of tumors which have grown within or into the blood-ves sels, air-,lobules, fat-globules, etc.
The effects caused by arterial embolism are: First, a transient ancemia of the ter ritory supplied by the occluded artery, which may pass away without leaving any permanent consequences. Secondly, necrosis of this territory, which may be either sudden, in the form of gangrene, or more gradual, in the form of softening or Thirdly, the formation of an hremorrhagic infarction or congestion of the territory, followed by extravasation of blood into the tissues and the formation of a firm, solid, wedge-shaped patch of dark-red color. the apex of the wedge toward the embolus and the base toward the periphery. In the brain and other very soft organs the extravasation may disintegrate the tissue and cause the or dinary phenomena of an apoplectic clot. These hemorrhagic infarcts may undergo a variety of changes. Degeneration usu ally sets in, the patch becomes more or less deeolorized, undergoes molecular dis integration, contracts, and finally leaves a depressed fibrous patch in which the re mains of the altered blood may often be recognized. Again. the patch may soften down into a puriform fluid, which may become enveloped by a fibrous capsule, and ultimately dry up or become the seat of calcareous deposit. These patches, when recent, are generally surrounded by a zone of congested vessels.