8 NOTE ON THE DIGESTION OF MINERAL SUBSTANCES. 
ing function of the skin at this part. In ordinary conditions 
this exalted activity is productive of no evil result; but when 
it chances to occur very suddenly, in consequence of a too- 
nutritive alimentation, it gives rise to disease. For instance, 
when wheat, or barley, or any other very alible grain, is given 
in undue quantity, acute laminitis not unfrequently ensues.* 
Indeed, from pathological observation there often appears to 
be a close sympathy in this respect between the mucous 
membrane lining the alimentary canal, the skin, and the 
membranes of the foot. 
(To be continued .) 
NOTE ON THE DIGESTION OF MINERAL 
SUBSTANCES. 
By Richard V. Tuson, F.C.S., Professor of Chemistry at 
the Royal Veterinary College. 
Physiologists and chemists have hitherto entertained the 
belief that the principal if not the sole function of the pep- 
sin and acid contained in the gastric juice is to render solu¬ 
ble the albumenoid constituents of food, and thus prepare 
them for the subsequent process of absorption. 
Conceiving, however, that it would be extremely interest¬ 
ing to study the effect, if any, of the solvent constituents of 
the gastric juice upon substances, especially those employed 
as medicines, I have set myself the task of investigating this 
subject. The inquiry is as yet but in its infancy, neverthe¬ 
less the results already obtained are sufficiently positive and 
striking to induce me to “ claim date” by placing on record 
the following experiments: 
Experiment 1.—A mixture of calomel j* and distilled water 
containing 2 per cent, of hydrochloric acid. 
Experiment 2.—A mixture of calomel, pepsin,J and dis¬ 
tilled water. 
Experiment 3.—A mixture of calomel, pepsin, and dis¬ 
tilled water containing 2 per cent, of hydrochloric acid. 
These mixtures were placed in glass vessels, and kept at 
38° C. (10(>2 o F.), i.e. about the temperature of the body, 
for twenty-four hours, during which time they were occasion¬ 
ally stirred or shaken. They were then thrown on to filters 
* During the recent siege of Paris, numerous cases of laminitis were 
observed ; they were due to the use of barley as forage. 
f The calomel employed in all the experiments was previously tested as 
to its purity. 
J Pepsina porci prepared by Messrs. Bullock and Reynolds, 
