FRANKLIN C. McLEAN 



PEKING * ', 



Introduction 



Definition. Edema is a local or general condition, characterized by 

 the presence of abnormally large amounts of fluid outside of the vascular 

 system. The fluid resembles normal lymph in composition, and is usually 

 found in the intercellular spaces or serous cavities, but an increase in the 

 intracellular fluids may also occur. The condition results from a derange- 

 ment of the function which has to do with the continuous exchange of 

 fluids between the blood and tissues, and with the regulation of the volume 

 of the tissues. 



Historical. The clinical occurrence of edema and its relation to a 

 diminished output of urine have been recognized since the time of Hip- 

 pocrates, but it is only within the last century that any accurate knowledge 

 concerning the condition, in its relation to the disturbances which cause 

 it, has been accumulated. Especially within the past thirty years an 

 enormous literature on the subject has become available, and much prog- 

 ress has been made towards arriving at a more complete understanding 

 of the various factors concerning its pathology. 



The present knowledge of the mechanism of the occurrence of edema, 

 and even of the process of normal lymph production, is far from satis- 

 factory, in spite of the progress which has been made. Certain funda- 

 mental problems, such as the relation of the excretory function of the 

 kidneys to edema, are still unsolved. It is necessary, therefore, to treat 

 the whole subject of edema as a problem, the final solution of which has 

 not yet been reached. It is of interest to review the historical development 

 of this problem, especially with reference to the trend of thought re- 

 lating to it. 



Bright (a), in 1S27, recognized the association of edema with disease of 

 the kidneys, manifested clinically by albuminuria, and at autopsy by 

 definite pathological changes in these organs. He also recognized the 

 occurrence of a diminished protein content in the blood serum and sug- 

 gested the probability of a disturbance in the healthy balance of the 



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