chemical correspondence between these various substances and those which are akin to them. Thus:
| Carbon. | Hydrogen. | Oxygen. | ||
| Starch | ||||
| Dextrine | ||||
| Cellulose | 12 | 10 | 10 | |
| Lignine or woody matters | ||||
| Gum | ||||
| Cane sugar | 12 | 11 | 11 | |
| Grape-sugar | 12 | 12 | 12 | |
| Amyloid substance | ||||
| Lactic acid | 6 | 6 | 6 | |
There is no difficulty, therefore, in understanding, to some extent, how it is that, under the action of pepsin, or diastase, or some other ferment, starch, and dextrine, and cellulose, and lignine, and gum, and cane-sugar, and grape-sugar, and amyloid substance, may be transformed into the lactic acid which forms so important an ingredient in gastric juice, and that the lactic acid so formed, after having done its work in digesting nitrogenous substances, may be absorbed into the circulation directly, and be there disposed of in oxidization as a very readily inflammable fuel—perhaps as the more readily inflammable of all the force-fuels. And certainly there is no reason to believe that amyloid substance or sugar is more inflammable than lactic acid, but rather the contrary, for lactic acid can not be traced, as amyloid substance and sugar can be, beyond the limits of the alimentary canal. In any case I am, I think, at liberty to assume that a good deal of starch and sugar, and of the articles akin to them, are of great use in supplying lactic acid, and that this lactic acid has to do very important work, not only in the primary processes of digestion, but also as force fuel.
C. If this be so, the effect of taking sour buttermilk, sour milk, and sour whey—the sourness of which depends upon the presence of lactic acid—ought to be unequivocally beneficial in many cases.
M. So it is. I have long been in the habit of recommending these articles in cases where the digestive power is feeble and the circulation wanting in vigor, and I am quite satisfied that the practice is very satisfactory in its results. Instead of being "a weight to the stomach," as fresh milk often is said to be in these cases, these drinks are generally found to facilitate digestion and to keep up the warmth of the system. Indeed, by using sour buttermilk and sour whey, I have often found it possible to leave off doses like rum-and-milk, and to do without alcoholic drinks altogether.
C. I am prepared to believe what you say by what I know of the experience of those who take sour milk or sour buttermilk habitually, or who have tried the whey-cure. I have more than once heard an Irish peasant say that he misses the sour milk he takes along with his potatoes almost as much as the potatoes themselves, and that "it
