Defervescence in rheumatic fever takes place, as a very general rule, gradually--_i.e._ by lysis--but exceptionally it is completed in forty-eight or even twenty-four hours. An interesting observation, which will be of much prognostic value if it be confirmed hereafter, has been made by Reginald Southey,[33] to the effect "that a short period of defervescence, or a sudden remission and an early remission, betokens the relapsing form of the disease, and the likelihood of frequent relapses, as well as of slow ultimate recovery, in the direct ratio as this defervescence has been early and abrupt." [Footnote 33: _St. Bartholomew's Hospital Reports_, xiv. p. 16.] {30} The characters of the urine in acute rheumatism are tolerably uniform, but far from constantly so. Its quantity in the majority of cases is reduced, frequently not exceeding twenty-four ounces per diem, and occasionally not exceeding fourteen. This is owing in some degree to profuse sweating, but also, as in other febrile affections, to retention of water. Its density is usually high--1020 to 1030, or even 1035--which is due chiefly to its concentration, and not, as has been generally supposed, mainly to an increase in the total solids excreted.[34] Its color is a very dark red or deep reddish-yellow, partly from concentration; but it is yet not known whether the deep hue is partly from increase of the normal pigments or of one of them (urobilin),[35] or from the presence of some abnormal coloring matter. Its reaction is generally highly acid, and continues so for many hours after its discharge, unless in subacute cases, when it is occasionally neutral or sometimes alkaline at the time of its escape, or becomes so in a very short time afterward. It is commonly toward the decline of the attack that the urine becomes neutral or alkaline. As a very general rule, the amount of urea and of uric acid excreted during the febrile stage exceeds what is physiological, and begins to decline when convalescence commences; but this may be reversed (Parkes,[36] Lede,[37] Marrot[38]). The sulphuric acid is notably increased (Parkes), the chlorides often diminished and sometimes absent, and the phosphoric acid very variable (Beneke, Brattler[39]), but usually lessened (Marrot). [Footnote 34: See _Guy's Hospital Reports_, 3d Series, vol. xii. 441.] [Footnote 35: Jaffe, _Virchow's Archiv_, xlvii. 405, quoted in _Ziemssen's Cyclopæd. Prac. Med._, xvi. 41.] [Footnote 36: _On Urine_, p. 286.] [Footnote 37: _Recherches sur l'Urine dans le Rheumatisme Artic. Aigue_, Paris, 1879.] [Footnote 38: _Contribution à l'Étude du Rheumatisme Artic., etc._, Paris, 1879, 41.] [Footnote 39: Quoted by Parkes, _op. cit._, 290.]