b. Chronic Dropsy is that which more usually attends upon cardiac or renal disease. We also find either oedema of the feet and ankles, or still more general anasarca, depending simply upon deterioration of the blood, with excess of serum.
Of this the most common causes are: 1. Exhausting diseases —phthisis, dancer, chronic bronchitis (when not acting, as it com monly does, through the medium of the heart, the first part of the circulatory apparatus affected by obstruction in the lungs), disease of the liver, especially when associated with ascites. 2. Want of food or improper nutrition. 3. General poverty of blood, as in anaemia and chlorosis. The diagnosis of these dis orders will be considered in their proper places in the sequel; but we may learn, from their number and variety, how false is that theory which is expressed in the terms cardiac and renal dropsy. Disease of either organ may aid in its production, but probably in every case blood changes must have occurred before the serum exudes through the coats of the capillaries.
c. When local, the term oedema is more commonly applied than anasarca. The cause must be referred to some obstruction to the returning current of the blood, pressure on the veins from with out, or occlusion from within; an unnatural condition of the parts through which the venous trunk passes, or inflammation of its internal coat. The extent of surface cedematous, and a refe rence to the distribution of its bloodvessels, will greatly aid in determining in what portion of its current the blood is obstructed. Acute phlebitis is almost always associated with cedema, but the occlusion may also be one of long standing. When obstruction is produced by pressure, and its cause is situated externally to the great cavities of the chest and abdomen, the diagnosis must be extremely simple; but when• the pressure is occasioned by some tumor lying within, it is oftentimes made out only with ex treme difficulty, and by very careful examination.
Local cedema also accompanies inflammations of limited extent, whether in the skin, such as erythema and erysipelas, or the dif fuse inflammation of the cellular tissue, or even suppurations of the bones, joints, and ligaments ; and cases will occur in which it is difficult to determine whether the inflammation of the skin and cellular tissue were caused by some irritation of a limb already tense from cedema, or the effusion of serum were the consequence of the local inflammation.
§ 2. as has been stated, upon more than one cause as its source, and demanding treatment often distinct from that of the disease from which it springs, ascites claims our notice when it is either unassociated with anasarca, or itself forms much the most prominent feature of a case in which there is more or less general dropsy. In rare instances, too, it appears to have sprung from some transient morbid state, and to persist merely because the accumulation of fluid, by its pressure, prevents the due action of the absorbent and eliminating process by which it might be removed.
When associated with anasarca, it is very important to deter mine whether it is to be classed as one of the many local -effusions which acknowledge the same general causes; or as having an independent origin and cause, which simply co-exist with the others; or lastly, whether the anasarca may not itself be only the consequence of the ascites. The history, if absolutely correct, would always decide the first and last of these questions, espe cially if taken in connection with the inquiry, which ought never to be omitted, into the several conditions of system usually asso ciated with general dropsy. When these have been for some time in operation, and cedema has been observed distinctly prior to effusion into the abdominal cavity, the presumption is strong that ascites is merely casual and coincident, an evidence of a general tendency. When, on the other hand, fluid has been first detected in the peritoneum, and the more commonly acknowledged causes of anasarca are absent, it is highly probable that an oedematous state of the lower limbs is caused only by obstruction to the returning column of blood through the distended cavity, in an impoverished state of system. Unfortunately it very often hap that accumulations either of flatus or of fece,s are mistaken rdropsical swelling, or that the enlargement of the abdomen is not taken notice of until after anasaroa has supervened : it is, therefore, very generally necessary t,o inquire into the causes of each condition separately, and not to rest satisfied with the hypo thesis that they are both part of the same disease.