The following table, containing the results of Lehmann on different forms of diet, as affecting the daily amount of the various solid matters discharged by the urine, is a very important ad dition to our knowledge of this subject : — Severe and continued bodily exercise was found by Lehmann to increase the discharge of urea, lactic acid, phosphates, and sulphates. He observed a diminution, however, in the proportion of uric acid and extractives dis charged under the same conditions.
Simon, simultaneously with Lehmann, as certained that the amount of urea, sulphates, and phosphates excreted, is increased by strong bodily exercise. Simon remarks upon this result :—" Further confirmation of the above observation is certainly desirable. If, however, we might assume it as a general fact, it would be an additional argument in favour of my view regarding the formation of urea ; for it would then become still clearer that the urea is not formed during the change which occurs in the blood as a consequence of peripheral nutrition, but that it is formed during those processes which are dependent on the respiratory and circulatory functions, in which we must seek for the greater part of the carbonic acid which is exhaled, and for the principal source of animal heat. I refer to the active metamorphosis of the blood, or to the mutual action excited by the blood corpuscles, the plasma, and the oxygen held in solution in the blood, on each other." Dr. Percy has made experiments corro borative of the views of Simon. He did not, however, observe any augmentation of the soluble salts, viz. phosphates, sulphates, and chlorides.
In relation to this subject, Simon alludes to the opinion expressed by Berzelius, that at least a portion of the sulphates and phosphates occurring in the urine, are derived from the oxidation of phosphorus and sulphur which previously existed as components of protein compounds, which become changed during the metamorphosis of the blood. This view I
hold to be especially true as respects the phosphates, and would here refer the reader to a paper of mine printed in the Philoso phical Magazine #, in which I showed that the amount of alkaline phosphate contained in the serum of arterial blood is much greater than in that of venous, and that the amount of such salt in venous serum can be at once increased by exposing the blood corpuscles to air, and consequently to the action of oxygen during the coagulation of the fluid.
I feel satisfied, indeed, from my results, that one great and essential difference between arterial and venous blood consists in the great excess of alkaline phosphate contained in the serum of the blood of the arteries'as compared with that of the veins.
With respect to the quantity of chloride of sodium excreted by the urine, it is subject to great variation. Simon remarks, that the urine in disease is sometimes deficient in salts, and that this deficiency takes place at the expense of the chloride of sodium. He found but a trace of chloride of sodium in the urine of a patient suffering from typhus.
Dr. Bence Jones has made experiments on the variation of the sulphates in urine, and has arrived at the following conclusions : 1. The sulphates are increased by food, both animal and vegetable.
2. Exercise does not produce so marked an increase in the sulphates.
3. Sulphuric acid in large doses increases the proportion of sulphates ; in small doses it produces little or no effect.
4. Sulphur, when taken, increases the sul phates in the urine, and sulphate of soda or magnesia produces the greatest effect on the quantity of the urine.
With respect to the phosphates contained in the urine, Dr. Jones has arrived at the conclusion, that the quantity of phos phates depends on the quantity contained in the ingesta, and that this is also the case with the alkaline phosphates. These latter, how ever, are to a certain extent increased by exercise.