446 THIRD CLASS OF MINERAL CONSTITUENTS. 



I placed pure gluten, with milk-sugar and a little oil, in a dilute 

 solution of sulphate of potash, and kept the mixture at a blood- 

 heat, the mass first underwent the lactic fermentation, very soon 

 became putrid, and, in the course of 6 or 8 days, unmistakeably 

 developed sulphuretted hydrogen ; in this way I was enabled, by 

 the gradual addition of acetic acid, to remove the whole of the sul- 

 phuric acid from a mixture to which I had added 5 grammes of 

 sulphate of potash. That the sulphate is, in like manner, de- 

 oxidised into the sulphide in the intestinal canal, where similar 

 substances are brought in contact, is obvious from the composition 

 of the stools which are discharged after the use of mineral waters, 

 containing (like those of Marianbad) both sulphate of soda and car- 

 bonate of protoxide of iron. 



In these feeces, which are usually green or black, I have recog- 

 nised with certainty the presence of the sulphide of iron, but not 

 of the bisulphide, as Kersten* seems to have done. 



That the amount of sulphuric acid in the urine is chiefly due 

 to the decomposition and oxidation of tissues containing sulphur is 

 obvious from a comparison of the sulphates taken with the food 

 and of those discharged by the urine. 



As a mean of numerous experimentsf, I found that the sul- 

 phates discharged with the urine amounted daily to 7*026 grammes, 

 while I was living on an ordinary mixed diet. After a strictly 

 animal diet for 12 days, the sulphates rose to 10*399 grammes ; 

 and, after the use of a strictly vegetable diet, they fell to 5*846 

 grammes. During these experiments I drank nothing to allay my 

 thirst but common spring water, which, besides a little gypsum, 

 contained only small quantities of alkaline sulphates ; so that the 

 striking difference in the amount of the excreted sulphates could 

 not be traced to that head. Moreover, the extraordinary augment- 

 ation of the urea in the urine excreted during my animal diet 

 indicated that this corresponding augmentation of the sulphates 

 depended on the same cause, namely, on a decomposition and 

 oxidation of the substances taken as food. 



CARBONATE OF MAGNESIA. 



This earthy salt occurs only sparingly in the animal organism. 

 According to BerzeliusJ, it is not improbable that the magnesia in 



* Journ. f. Chirtirgie von Walther und Ammon. Bd. 2, S. 2. 

 t Journ. f. pr. Chem. Bd. 25, S. 2, and Bd. 27, S. 257- 

 t Lehrb. d. Chem. Bd. 9, S. 545. 



