ALKALINISERS OF THE URINE. 513 



excretes it as the carbonate. Soda does, however, possess a 

 degree of specific action on the kidney, especially its Phosphate 

 and Acetate. Lithia closely resembles Potash in this respect ; 

 Ammonia, although not an alkaliniser, has a similar influence ; 

 and Magnesia and Lime are distinctly stimulants of the renal 

 epithelium, as is well seen in some natural mineral 

 waters. Now, in passing through the cells, these salts 

 necessarily carry with them a certain amount of water from 

 the venous pl6xus around the tubules, and if abundant, actually 

 produce diuresis. They thus furnish us with another group of 

 diuretic measures, which we call the saline diuretics, chiefly 

 alkaline in their influence on the blood and urine, but at the 

 same time independently active as specific renal stimulants. 

 Let it be carefully noted that the saline diuretics do not, as far 

 as we know, directly affect the renal circulation ; but that we 

 possess in them an indirect means of influencing the venous 

 plexus around the tubules, and thus the whole renal 

 circulation and the general blood pressure, especially the 

 pressure in the veins. 



Another great group of natural substances in the materia 

 medica have a specific effect on the renal epithelium, namely, 

 the Aromatic Oils, Oleo-resins, and Balsams. The chief of 

 these are Turpentine, Juniper, Copaiba, Cubebs, Cantharides, 

 and Hops ; whilst Jaborandi, Alcohol, Aconite, and many more act 

 partly in the same way. All these substances, either as such or 

 after decomposition, are excreted (in part) by the renal cells, 

 and carry with them, like salines, so much water, besides 

 dilating the renal vessels, as we have already seen. The degree 

 in which the different members of this great class act upon the 

 renal cells varies widely, however : thus, Juniper and Copaiba 

 are powerful diuretics, greatly increasing the urinary flow, 

 whilst most of the others have but little effect on the volume of 

 urine, possibly because their action on the renal vessels, which 

 accompanies their action on the cells, does not favour the escape 

 of fluid. Thus Turpentine and Cantharides, two most powerful 

 renal stimulants, sometimes diminish, sometimes increase, the 

 urinary water, and may even cause haemorrhage from the 

 glomerulus. 



Opposed to these renal stimulants are renal sedatives or 

 depressants, which appear to diminish directly the activity of 

 the renal cells, when they reach them through the blood. 

 Morphia has this effect, and possibly quinia ('r) and other sub- 

 stances. 



III. PATHOLOGICAL RELATIONS. 



The disorders of the renal functions, which will be taken by 

 2 H 8 



