Of all the hypotheses that have been advanced to account for the nature of the morbid state, which gives rise to general and local dropsy, there are only three which our author regards as entitled to our notice. According to these, all dropsical accumulations arise either, 1st, From a want of tone or energy in the absorbent vessels, giving rise to a deficient absorption. 2nd, From an increased exhalation of the natural fluid, through a similar want of tone in the exhalents; and 3d, From a mechanical obstruction to the free return of blood by the veins, produced by tumours of various kinds, &c., by which a greater portion of it is forced into the exhalents, and a greater effusion of their proper fluids thereby occasioned. With these hypotheses, however, Dr. AYRE is not satisfied, and he endeavours, in the following manner, to show their insufficiency. "1st. The opinion of a want of tone in the absorbents, as a cause of dropsy, is contradicted by the fact, that in those cases, in which it is assumed to prevail, it is found, that the adipose matter, or fat of the body, is removed by the absorbents; or, in other words, that emaciation takes place to as great an extent, and as rapidly in this, as in other diseases; and emaciation can only be effected by means of absorption. Besides, in these cases of dropsy, mercury, when rubbed upon the surface, or received internally, is absorbed as readily, and affects the system as early as under other states of the body. There is also no accumulation of the fluids in the joints, or in the _bursae mucosae_ in these cases, which, nevertheless would happen, if there was a general debility of the absorbent system; and _ecchymoses_ or livid spots, though easily induced in anasarcous limbs, are likewise easily removed from them by the absorbents. "2nd. The opinion of a want of tone or energy in the exhalants involves in it one of the following conditions: namely, either, 1st, that the fluid of dropsy may escape mechanically from them, and that the fluid thus _mechanically_ separated may be identified in its sensible and chemical qualities with another fluid which is confessedly secreted; or 2nd, that if the fluid of dropsy be secreted, then that an _increase_ in the quantity of a secretion may continue an indefinite period, under a _decrease_ in the energy of its secreting vessels; conclusions to which experience and analogy are alike opposed." In answer to the third hypothesis, Dr. A. remarks, that such an obstruction as contemplated, has never been shown to exist.