Water in large quantities. Carbonic acid (aerated waters), Sodium salts, e.g. common salt.

Potassium salts, Acetate. Bitartrate. Chlorate.

especially the Citrate. Nitrate.

Hydragogue Diuretics.

Adonis Vernalis.

Broom.

Caffeine.

Colchicum.

Digitalis.

Erythrophloeum. Nitrous ether. Squill. Strophanthus.

1 Jendrassik, Deutsch Archiv f. klin. Med., xxxviii. p. 499.

2 Locke, Practitioner, xxxvii. p. 170.

3 Riegel, Verhandl. d. III. Congress f. inner. Med., 1884.

4 Von Schroeder, Central. f. d. med. Wiss., 1886, p. 465; Langgard, ibid. p. 513.

Stimulant Diuretics.

Alcohol.

Gin.

Hock. Cantharides. Blatta Orientalis. Oleo-resins, resins and volatile oils Turpentine.

Juniper.

Savin. Copaiba. Cubebs. Black pepper. Matico. Kawa. Guaiac.

Umbelliferous plants chiefly containing volatile oils Parsley.

Carrot.

Dill.

Fennel. Cruciferous plants Mustard.

Horseradish.

Asparagus. Uva ursi. Sarsaparilla. Buchu. Pareira. Chimaphila. Taraxacum. Ononis spinosum. Santonica.

The following tabular view of the probable mode of action of the various diuretics may help to show it more distinctly:-

Diuretics.

Raise arterial pressure....

Generally

Digitalis.

Increased action of the heart

digitalis

Erythrophloeum.

alcohol.

Strophanthus.

Contraction of vessels in intestine and through-out the body.

Squill.

Convallaria.

Strychnine.

Caffeine (p. 432).

Cold to surface.

Contract efferent vessels or arteriae rectae so as to raise pressure in glomerulus and lessen absorption in tubules, or both.

By action on vasomotor centres.

? The same as in preceding list.

Locally in kidney.

By local action on vessels or nervous structures in the kidney itself.

? Broom.

? Turpentine.

? Juniper.

? Copaiba.

? Cantharides.

Dilate afferent vessels.

Paralyse vaso-motor nerves or involuntary muscular fibre, or stimulate vasodilating nerves.

Nitrites.

Alcohol.

? Urea.1

Act on the secreting nerves, or secreting cells of the kidney itself.

Increase water excreted.

Urea.

Caffeine.

Calomel.

Increase solids excreted.

Liquor potassae.

Potassium acetate, etc., and other saline diuretics.

Uses. - Diuretics may be employed for the purpose of removing either water or solids from the body. They are used :1st, to remove the excess of fluid met with in the tissues and serous cavities in cases of dropsy.

2nd, to hasten the removal of injurious waste-products and poisonous substances from the blood.

3rd, to dilute the urine.

1 When a current of blood is passed artificially through an excised kidney, the stream is much accelerated by the addition of urea. Abeles, Sitz.-Ber. d. k. k. Wiener Akad., Bd. 87, Abt. 3, April 1883.

In cases where the accumulation of fluid depends on venous congestion, as for example in cardiac dropsy, those diuretics which act on the general vascular system, like digitalis, strophantus, squill, or erythrophlceum, are most efficient because they tend to remove the cause of the dropsy (p. 333), as well as to assist the absorption and excretion of the fluid already effused.

When the dropsy depends on the disease of the kidneys or liver, other diuretics should either be given instead of, or along with, digitalis or squill. Even in cases of cardiac disease where digitalis or squill are not proving efficacious, the addition of a little blue pill greatly assists their action, though it would be hard to say in what way it does so.

In dropsy depending on kidney disease, decoction of broom, oil of juniper, and nitrous ether are amongst the most reliable diuretics, and in hepatic dropsy, copaiba.

Diuretics are used to increase the secretion of solids in febrile conditions, and in cases of kidney disease where the excretion of waste-products is deficient, and their retention threatens to prove injurious. In such cases nitrate and bi-tartrate of potassium, turpentine, juniper, and caffeine are useful.

Diuretics are also used to increase the proportion of water in the urine, and thus to prevent the solids being deposited from it and forming calculi in the kidney or bladder, or even to dissolve again such concretions as have been already formed.

Adjuvants to Diuretics. - As the amount of urine secreted depends upon the difference in pressure between the blood in the glomeruli and the urine in the tubules, it is evident that any pressure on the tubules, whether caused by obstruction of the ureter by a calculus, by the mechanical pressure of dropsical accumulations in the abdomen, or by distension of the venous plexus in the kidney itself, will tend to lessen the secretion of urine. Consequently we sometimes find that in such cases diuretics fail to act until the pressure has been relieved by paracentesis in cases of dropsy, or the venous congestion lessened by the use of a brisk purgative, or by cupping over the loins.

If the venous congestion is very great, as in cases of mitral disease or of chronic bronchitis with emphysema and dilated heart, bleeding from the arm may be advantageous or even imperatively necessary. In dilated heart and in mitral incompetence, the action of digitalis on the heart itself, strengthening its action and enabling it more effectually to pump the blood out of the venous into the arterial system and thus reduce venous congestion, will aid its action upon the kidneys.

Action of Drugs on Albuminuria. - In the normal kidney no albumen passes from the vessels or lymphatics into the urinary tubules, but under abnormal conditions it may do so and the urine become albuminous.

Albuminuria may be produced by ligature or compression of the renal artery; by ligature of the renal vein; and, though to a less extent, by ligature of the ureter. A similar effect to that of ligature of the renal artery may be produced by causing it to contract temporarily by means of drugs such as digitalis. In the experiments made by Mr. Power and myself we noticed that the urine which was secreted after the secretion had been completely stopped by digitalis was albuminous.

Albuminuria is also noticed after poisoning by strychnine, which, as Grutzner has shown, has a similar action to digitalis, and in cases of suffocation or of epilepsy, where the vaso-motor centre is stimulated by venous blood.

Other drugs appear to cause albuminuria by a direct action on the kidney itself. A marked example of this is cantharides, which produces both albuminuria and haematuria. Shortly after its injection the kidney appears congested and swollen, and on microscopic examination it is found that the alterations begin first in the glomeruli and convoluted tubules, and gradually extend to the straight tubules. These changes consist in intense congestion, especially in the glomeruli, with increased tension of blood in the vessels. Then the liquid constituents of the blood pass through the vascular walls, carrying along with them granules, red corpuscles, and white corpuscles. This exudation then passes from the glomerulus along the whole length of the tubules, the epithelium of which next becomes changed, the cells which line them swelling up, multiplying, and becoming modified in form, migration of leucocytes also occurring. In short, we have the signs of inflammation beginning in the glomeruli and passing along the tubules.

Lead produces also disease of the kidney, but of a different kind. The kidney in animals poisoned by it is pale and granular with an adherent capsule and with atrophy of the cortical substance, in which crystals are often present. These appearances are due to chronic interstitial nephritis caused by calcareous deposits in Henle's loops. These block up the tubuli, produce subacute inflammation of the glomeruli and tubules, with atrophy and cirrhosis. A similar result is produced also by mercury. Chlorate of potassium has a very peculiar action on the kidney. In large doses it produces a peculiar kind of haematuria, the urine being dark brown and containing large quantities of broken-up blood-corpuscles. The drug arrests the secretion of the urine by blocking up the tubules with plugs of broken-up blood-corpuscles.

Tannin and tannate of sodium appear to have a certain power to lessen the exudation of albumen through the Mal-pighian tufts, as Ribbert found that when albuminuria was produced artificially in rabbits by temporary ligature of the renal artery, both tannin and tannate of sodium either lessened or prevented the exudation of albumen. Arbutin, the active principle of uva ursi, appears to be still more efficacious, but requires to be given in somewhat large doses. Fuchsin has a similar action.