(EDEMA AND DROPSY. 313 



increased transudation or diminished absorption. When there is an undue accumulation of 

 fluid more or less like serum in the lymph-spaces, we have the condition termed dropsy. When 

 there is general dropsy it is called anasarca.] 



(Edema. If the efferent veins and lymphatics of an organ be ligatured, or if resistance be 

 offered to the outflow of their contents, congestion and a copious transudation of lymph into 

 the tissue take place. These are most marked in the skin and subcutaneous cellular tissue. 

 The soft parts swell up, without pain or redness, and a doughy swelling, which pits on pressure 

 with the finger, results. These are the signs of lymph-congestion, which is called oedema 

 when the fluid is ivatery and localised. 



Under similar circumstances lymph is effused in the serous cavities. [In the peritoneum it 

 is ascites thorax, hydro-thorax pericardium, hydro-pericardium cranium, hydrocephalus 

 tunica vaginalis, hydrocele joints, hydrarthrosis, &c] If, at the same time, a large 

 number of colourless blood-corpuscles pass out of the blood-vessels into the cavity, the fluid 

 becomes more and more like pus. In order that these corpuscles may proliferate, a consider- 

 able percentage of albumin is necessary. When the pressure within the serous cavity rises 

 above that in the small blood-vessels, water may pass into the blood. These sero-purulent 

 effusions not unfrequently undergo changes, and yield decomposition-products, such as 

 leucin, tyrosin, xanthin, kreatin, kreatinin (?), uric acid (?), urea. Endothelium from the 

 serous cavity, sugar in pleuritic effusions and in cedemas with little albumin, cholesterin 

 frequently in hydrocele fluid, and succinic acid in the fluid of echinococci have all been found 

 in these effusions. The effusion of lymph may arise not only from pressure upon the lym- 

 phatics, but also from inflammation and thrombosis of the lymphatics themselves, in which 

 cases not unfrequently new lymphatics are formed, so that the communication is re-established. 

 Sometimes the ductus thoracicus bursts, and lymph is poured directly into the abdomen or 

 thorax. [Ligature of the thoracic duct results in rupture of the receptaculum chyli and escape 

 of chyle and lymph into the large serous cavities (Ludwig).] 



When dropsy or effusion of fluids occurs into serous cavities, there is always a greater 

 transudation of fluid through the blood-vessels. The abdominal blood-vessels, and those which 

 yield a watery effusion under normal circumstances, are those most liable to be affected. 



Transudation is favoured by (1) Venous congestion, so as to raise the blood-pressure, in 

 which case the effusion usually contains little albumin and few lymph-corpuscles, while the 

 coloured corpuscles, on the contrary, are more numerous the greater the venous obstruction. 

 Ranvier produced oedema artificially by ligaturing the vena cava in a dog, and at the same time 

 dividing the sciatic nerve. The paralytic dilatation of the blood-vessels thereby produced 

 caused an increased amount of blood to pass to the limb, while the blood-pressure was raised, 

 and both factors favoured the transudation of fluid. [Ranvier's experiment proves that mere 

 ligature of the venous trunk of a limb by itself is not sufficient to cause oedema. The oedema 

 is due to the concomitant paralysis of the vaso-motor nerves. If the motor roots of the sciatic 

 nerve alone be divided along with ligature of the vena cava, no cedema occurs, but if the vaso- 

 motor fibres are divided at the same time, the limb rapidly becomes oedematous. There is such 

 an increased transudation through the vascular walls that the veins and lymphatics cannot 

 remove it with sufficient rapidity, and oedema occurs. If there be weakness of the vaso-motor 

 nerves, slight obstruction is sufficient to produce oedema.] When the leg- veins are occluded 

 with an injection of gypsum, cedema occurs. (2) Some unknown physical changes occur in the 

 protoplasm of the endothelium of the capillaries and blood-vessels, which favour the transudation 

 of albumin, haemoglobin, and even blood-corpuscles. This occurs when abnormal substances 

 accumulate in the blood e.g., dissolved haemoglobin and when the blood contains little or 

 albumin. The same has been observed after exposure to too high temperatures, and the swelling 

 of soft parts in the neighbourhood of an inflammatory focus seems due to the transudation of fluid 

 through the altered vascular wall. It is probable that a nervous influence may affect particular 

 areas through its action on the blood-vessels of the part (it may be upon the protoplasm of the 

 blood-capillaries). The transudations of this nature usually contain much albumin and many 

 lymph-corpuscles. (3) When the blood contains a very large amount of water, the tendency to 

 transudation of fluid is increased. After a time it may produce the changes indicated in (2), 

 and when long continued may increase the permeability of the vascular wall. Watery lym- 

 phatic effusions from watery blood " cachectic oedema " occur in feeble and badly-nourished 

 individuals. [One of the commonest forms of dropsy is the slight oedema of the legs in anaemic 

 persons, in whom the heart and lungs are healthy. Many factors are involved the blood - 

 pressure, watery condition of the blood, the condition of nutrition of the capillaries, and 

 probably a tendency to vaso-motor paresis (Brunton).] 



[The fluid poured out varies according to the rapidity with which this occurs. In acute 

 inflammations effusion or exudation takes place rapidly, and the fluid contains the fibrin-factors, 

 so that it tends to coagulate spontaneously. There is every gradation between the non-coagulable 

 hydrocele fluid and the coagulable exudation in inflammation. The fluids in different dropsies 

 vary in composition, and some have more cells in them, depending on local causes, as in some 

 situations absorption is more active than in others. The pleural fluid contains most solids, 

 then ascitic, cerebro-spinal, and lastly that in the subcutaneous tissue. Transudation cor- 



