In the case of uratic renal concretions conditions are altogether different. Here an endeavor must be made to reduce the production of uric acid to a minimum, as in arthritis urica, and in addition to increase the solubility of uric acid in the urine to a maximum. This is particularly important in these patients as against cases suffering with gout, because the latter are predisposed to an abnormally large production of uric acid (see Vol. VIII). One of the most valuable means we possess to produce better solubility of urinary uric acid is an abundance of liquids, because the latter render the urine dilute; in addition a certain amount of alkalie is necessary; for, while alkalies rather solidify than dissolve acid sodium urate as it occurs in tophi, they act as a powerful solvent for free uric acid. It is doubtful, of course, whether it is possible to dissolve the dense granules of a larger concretion consisting of a consolidated conglomerate of free uric acid in the renal pelvis, but it is probable, nevertheless, that a certain amount of loosening and disintegration of larger conglomerates to smaller ones can be produced. So much is certain that uric acid, that has not yet formed such solid conglomerations, can be prevented from precipitating by changes brought about in the reaction of the urine. In other words, further concretions can be prevented, although it is not certain by any means that concretions already formed can be redissolved. It is hence very important to counteract too great degrees of acidity of the urine. Hence nephrolithiasis will always be a fruitful field for alkalie therapy carried out by the continuous administration of small quantities of alkaline salts, of alkaline waters, or by a sojourn at some watering place with alkaline springs.

It is, of course, necessary to prevent the urine from becoming alkaline; for it is well known that earthy phosphates are very apt to precipitate upon uric acid concretions as soon as the reaction of the urine turns alkaline. In my earliest publications on this subject I called attention to the advisability of studying the individual acid curve of the urine as a preliminary step and to regulate the quantity and the administration of alkaline remedies on this basis. (Ueber die Beeinflussung der Harnreaktion. Munchener mediz. Wochenschrift. 1888. Nr. 39.) I have frequently had occasion later to note that this is the correct way of proceeding and a very important preliminary step, for I frequently saw patients seriously injured by the routine administration of alkalies without such careful initial studies. In the meantime, my attention was called to the importance of calcium carbonate in the treatment of uratic concretions. The investigations of A. Ritter and others had shown that the power of the urine to hold uric acid in solution was essentially dependent upon the relative proportion of mono-sodium phosphate and disodium phosphate present in the urine. The former precipitates uric acid; the latter readily dissolves it. If calcium is administered a large portion of the phosphates contained in the diet is fixed in the form of insoluble calcium phosphate in the intestine, another portion is assimilated but is reëxcreted into the bowel via the intestinal mucosa in combination with calcium. This leads to a great decrease of the total phosphates in the urine and, as has been shown experimentally, of the mono-sodium phosphate that is particularly detrimental. Even though very formidable quantities of calcium are administered, an alkaline reaction is never produced in the urine. (Von Noorden, Zur Behandlung der harnsauren Nieren-konkremente. Kongress für innere Medizin. Wiesbaden, 1896. p. 308: - also the publications of my pupils, /. Strauss, Zeitschr. für klin. Med. Vol. 31, p. 492. 1897, and G. Herxheimer, Berl. klin. Wochenschr. 1897. Nr. 29.) Calcium carbonate is, therefore, an almost ideal method of prescribing alkalies in nephrolithiasis. This corresponds altogether with old empiric findings; for the waters that enjoy the greatest reputation in the treatment of nephrolithiasis are the waters of the Helen Spring, in Wildungen, Fachinger water, the waters of Contrexeville, and of recent years the waters of the Driburg Caspar Heinrich Spring, the Rudolf Spring, in Marienbad, the waters of Rohitsch. All these waters are distinguished by a high percentage of calcium (lime).

Of remedies that have been recommended urotropin acts in the same sense, that is, as a solvent for free uric acid. Nucleinic acid seems to possess the same property. Inasmuch as urea is capable of counteracting the precipitation of uric acid, nucleinic acid and urea have been united in a chemical compound that has been brought on the market under the name of Urol. All of these preparations, however, are far inferior in their effect upon the solubility of uric acid to calcium carbonate.

Whereas, we are capable by medicinal means of contributing a little to the solubility of uric acid concretions in the urinary passages, we are less able to exercise this effect upon the elimination of uric acid in genuine arthritis urica. The old established colchicum preparations seem to exercise such an effect, at least during the time of the attack, and to accelerate the critical outpouring of uric acid that accompanies gouty seizures. At other times than during the at tacks and in the free intervals of typical gout and in chronic atypical gout colchicum is altogether inert. It certainly seems worth while to study the effects of colchicum more carefully than heretofore. A remedy that has become so prominent purely empirically merits much more careful attention and study than has been given it in the publications of the last decades. Of salicylic acid and its derivatives, one can say positively that they favor the elimination of uric acid in gouty subjects, but it is a precarious matter to employ them for a long period of time. Salicylic acid is by no means without effect upon the kidneys, and the latter are always in danger in gout. Of recent years thymic acid, a derivative of nucleinic acid, is frequently found mentioned. It is said of this remedy that it materially favors the elimination of uric acid; the drug is known under the name of Solurol (daily dose 0.75 to 1.5 g.). So far our experience with this remedy is limited, and it is too early to draw any definite conclusions in regard to its efficacy. As far as we know to-day it is not practical to continue the use of Solurol for long periods of time, while, on the other hand, a course of treatment with Solurol, lasting about a week and repeated with interruptions from time to time, seems capable of causing the elimination of considerable quantities of retained uric acid.