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UNIVERSITY OF W ESTERN ONTARIO MEDICAL JOURNAL
to escape into the surrounding tissues. Inflammatory and anaphylactic oedema arise in this way and it is probable that oedema in the early stages of acute nephritis is the result of a diffuse capillaritis. The fourth factor is the qualitative and quantitative relationship between the electrolytes in the blood and tissue spaces. In certain forms of oedema, changes in the electrolyte pattern exert a profound influence. Fifth, the part played by the lymphatics which drain a portion of the intercellular fluid into the blood stream has received little attention. In addit ion, a nervous control exists which probably plays its role by exerting an influence over certain of the factors already mentioned. Finally, the relation of the endocrine glands to the mechanism of oedema must be considered, for in certain types they play an important part. We owe to Starling our knowledge of the importance of colloid osmotic pressure. It was he who first suggested that the exchange of fluids between the tiss ue spaces and the circulating blood is determined by the relative magnitude of two forces: (1) The hydrostatic pressure which tends to drive fluid f rom the blood vessels into the tissues; (2) The colloid osmotic pressure exerted by the plasma proteins which tends to draw fluid from the tissue spaces into the blood stream. Starling's theory receives ardent support from many investigators who have devoted considerable time and thought to this particular phase of the problem. It was given practical value by Epstein in explanation of the oedema of nephrosis, in which he found the plasma protein values to be low. It is interesting to recall that one hundred years ago Bright recognized that in certain forms of the disease which bears his name the blood was deficient in protein and suggested even at that time that albuminuria was the cause of oedema. According to Moore and Van Slyke, when the total plasma protein falls from the normal level of 6 to 8 grams % to 5.5 grams %, oedema is likely to occur. This, of course, is due to the decrease in colloid osmotic pressure exerted by the diminished plasma proteins. The most important protein in this regard is the albumen fraction, since it forms approximately 60 % of the total plasma proteins, and exerts, according to Govaert, four times as much osmotic pressure as the globulin fraction. Just as several factors enter into the mechanism of oedema, so several types of oedema may be recognized. It is well to keep these types in mind, and when confronted with an oedematous patient, an effort should be made to ascertain the exact cause of the swelling so that proper treatment may be instituted. The following modification of Christian's classification I have found helpful: TYPES OF OEDEMA:
1. Circulatory Failure Oedema-(a) Cardiac, (b) Hepatic. 2. Renal Oedema-(a) of Acute Nephritis, (b) of Renal Protein loss. 3. Nutritional Oedema-(a) Due to Plasma Protein Deficiency. (1) Diarrhoea, (2) Starvation, (3) Unbalanced Diet. (b) Due to Abnormality of Plasma Protein Formation. 4. Anaemic Oedema.