40 MATERIA MEDIC A AND THERAPEUTICS. 



blood is taken advantage of in the cases referred to under 

 potash, namely, gout and rheumatism, only less frequently; 

 for although soda is less depressing, as we shall see, than 

 potash, and more easily borne on the stomach, the slowness 

 of its entrance into the blood, and its tendency to pass off by 

 the bowels when the dose is increased, more than counteract 

 these advantages. When a prolonged and moderate alkaline 

 influence is desired, especially in dyspepsia with a tendency 

 to constipation, soda is manifestly to be preferred. 



3. SPECIFIC ACTION. 



In medicinal doses, the salts of soda have no specific in- 

 fluence on any organ. This circumstance, which at first 

 sight appears incredible, is due to the fact that the whole 

 organism is saturated with soda, which participates in many 

 of the ordinary tissue changes ; that soda is admitted 

 in large quantities by the food (especially vegetables and 

 fruits) ; and that the moderate amount contained in medicinal 

 doses does not appreciably affect metabolism. In this respect 

 soda differs remarkably from potash, and is therefore said to 

 produce none of the depressing effects of that drug. As we 

 have just seen, advantage is taken of this negative action of 

 soda in its therapeutical applications. 



4. REMOTE LOCAL ACTION AND USES. 



Soda is excreted by all the mucous surfaces, by the kidneys, 

 by the liver, and possibly by the skin ; and in passing through 

 the various epithelial structures, it increases their activity, 

 whilst it modifies the amount, composition, and reaction of 

 their secretions. The action of the different salts naturally 

 varies to a considerable extent, some affecting one organ more, 

 some another. The sulphate and the phosphate of soda are, as 

 we have seen, hydragogue purgatives by virtue of their imme- 

 diate local action ; but they are also stimulants of the intestinal 

 glands, and are constantly being absorbed and excreted, re- 

 absorbed and re-excreted, in their course along the bowel. (See 

 Part III.) Both are also true hepatic stimulants or direct 

 cholagogues '> the phosphate more so than the sulphate. The 

 value of these salts in hepatic and intestinal disorders, which 

 has been already referred to, is therefore partly referable to 

 their effect in increasing the bile. Soda tartarata has a similar 

 but feebler action. 



On the kidneys soda acts less powerfully as a diuretic than 

 potash, increasing the water and the solid constituents, and 

 diminishing or neutralising the acidity of the urine. The bi- 

 carbonate is the most useful salt of soda for this purpose ; the 



