Oedema(Gr., from to swell), a swelling occasioned, by the infiltration of serum into the areolar tissue of a portion of the body. The term oedema generally refers to cases in which the serous infiltration is local, as oedema of the face, of the extremities, of the lungs; anasarca to those in which it is general, invading the areolar tissue of the whole body. Anything which interferes with the return of the venous blood from a part may produce oedema; thus in pregnant women the pressure of the uterine tumor upon the great veins within the abdomen may cause oedema of the lower extremities; nd in feeble persons the same result follows the long maintenance of the upright position, the blood having to return against the force of gravity. Obliteration of any of the large venous trunks by adhesive inflammation is followed by oedema of the parts whose blood was returned by the obliterated trunk; thus phlegmasia dolens is caused by inflammation and plugging up of the femoral or iliac veins. The pressure of an aneurism or other tumor within the chest, upon the vena cava or vena innomi-nata, may produce oedema of one half or the whole of the upper part of the body.

Paralyzed limbs frequently become oedematous from the venous circulation no longer being aided by the contraction of the muscles of the part. Certain conditions of the blood, such as exist in chlorosis and scurvy, are favorable to the occurrence of oedema. In all these instances the oedema is of a passive kind; but the same symptom occurs as an attendant on some forms of inflammation, particularly a variety of erysipelas, hence termed oedematous erysipelas. In all instances oedema is simply a symptom produced by different causes, and is to be treated according to the cause by which it is produced. Two varieties of oedema, that of the glottis and that of the lungs, from their importance arising from the nature of the organs affected, deserve special mention. - (Edema of the glottis may occur from exposure to cold and moisture, as a consequence of tonsillitis and other affections, the inflammation extending to the larynx, or in the course of various diseases, as erysipelas, typhoid fever, etc. The patient is conscious of an increasing impediment in his respiration, and of a sense of stricture about the larynx. There is a dry hoarse cough coming on in paroxysms, with fits of suffocation, while the voice is hoarse, whispering, and finally extinct.

Inspiration is prolonged and difficult, while expiration is comparatively unaffected. Sometimes, but not invariably, there is soreness of the throat and difficulty of swallowing. The pulse, at first unaffected, as the difficulty of breathing increases becomes small and frequent, and the body is bathed in perspiration. Death from suffocation sometimes takes place a few hours after the commencement of the attack. On post-mortem examination the cellular tissue underneath the mucous membrane lining the glottis is found infiltrated by serum, narrowing the opening of the glottis and causing a sort of valvular action in inspiration. When violent the disease rarely leaves much time for treatment. Schonlein of Berlin first suggested the operation, but Dr. Gurdon Buck of New York was the first to carry it into effect, and has relieved numerous cases of this affection by nicking the oedematous mucous membrane, and thus giving exit to the effused serum which is the cause of the difficulty. When Dr. Buck's operation does not succeed, recourse must be had to tracheotomy. - (Edema of the lungs occurs in heart disease as a consequence of the embarrassed condition of the circulation through the lungs, in albuminuria (see Albuminuria), in typhus and typhoid fevers, in anaemia, and in pneumonia and bronchitis.

Its symptoms are difficulty of breathing, in some cases extreme, and a sensation of weight or constriction in the chest. There is teasing cough with a watery and sometimes viscid expectoration. On physical examination the percussion note is but slightly affected; auscultation gives a smooth, moist, fine, sub-crepitant rhonchus. The treatment is that of dropsy.