We could, for instance, intentionally discard digestion in the stomach, and thus transfer it to the bowel, by prescribing substances which do not excite the gastric glands. On the other hand, by lessening the acidity of the gastric juice we could reduce the activity of the pancreas, and these are matters which might be made use of in various special diseases, or even in some general disturbances of the digestive apparatus.

No less instructive is a comparison of the results of our experiments upon fat, with the demands of instinct and also with the precepts of dietetics and therapeutics. Everybody knows that fatty foods are heavy, that is, difficult of digestion, and in the case of weak stomachs they are usually avoided. We are now in a position to understand this physiologically. The existence of fat in large quantities in the chyme restrains in its own interest the further secretion of gastric juice, and thus impedes the digestion of proteid substances; consequently, a combination of fat and proteid-holding foods is particularly difficult to digest, and can only be borne by those who have good stomachs and keen appetites. The combination of bread and butter is less difficult, as might a priori be inferred from its wide employment. Bread requires for itself, especially when calculated per unit, but little gastric juice and but little acid, while the fat which excites the pancreatic gland insures a rich production of ferment both for itself and also for the starch and proteid of bread. Fat alone does not count by any means as a heavy food, as may be seen from the fact that large quantities of lard are consumed in certain districts of Russia with impunity.

This also is comprehensible, since the inhibitory influence of the fat in this case does not prevent the digestion of any other food-stuff, and is conducive to the assimilation of the fat itself. There is no struggle in this case between the several food constituents, and therefore no one of them suffers. In harmony also with daily experience the physician, in cases of weakness of the stomach, totally excludes fatty food and recommends meat of a fat-free kind; for example, game, etc. In pathological cases, however, where an excessive activity of the gastric glands is manifested, fatty food, or fat as emulsion, is prescribed. And here medicine has empirically brought to its aid the restraining action of fat, which we have so strikingly seen in our experiments.

Amongst all the articles of human food, milk takes a special position, and this is unanimously recognised, both in daily experience and in the practice of medicine. By everybody milk is considered a light food, and is given in cases of weak digestion as well as in a whole series of severe illnesses; for example, in heart and kidney affections. The extreme importance of this substance, a food prepared by Nature itself, we can now well understand. There are three properties of milk which secure it an exceptional position. As we already know, in comparison with nitrogenous equivalents of other foods, the weakest gastric juice and the smallest quantity of pancreatic fluid are poured out on milk; consequently, the secretory activity requisite for its assimilation is much less than with any other food-stuff. In addition, milk possesses a further important property. Thus, when it is introduced unobserved into the stomach of an animal it causes a secretion both in the stomach and also one from the pancreas; consequently, it appears to be an independent chemical excitant of the digestive canal; and in this action it is remarkable that we perceive no essential difference in the effect when the milk is brought unnoticed into the stomach from that which occurs when it is given to the animal to lap.

Although flesh is a better chemical excitant, it is by no means a matter of indifference how it gets into the stomach. It must, therefore, be accepted that milk excites not only a really effective, but at the same time a very economic, secretion, and also that the appetite is unable to stimulate this secretion into a more active or abundant flow. The secret of the relation of milk to the secretion of the digestive juices can, unfortunately, at present be submitted to no further analysis or investigation. We are at liberty, however, to suppose that the fat on the one hand is of importance for the inhibition of the gastric glands, and the alkalinity on the other for the restraint of the pancreas. Thus the gastric glands and the pancreas, notwithstanding the presence of excitants, are maintained by milk at a certain but not too high degree of activity, a matter which is in every way desirable in consideration of the easy digestibility of its constituents. Finally, the third characteristic which is observed to belong to milk, and which is probably only an expression of the first, consists in the following.

When one administers to an animal equivalent quantities of nitrogen, in the one case as milk, in the other as bread, and afterwards estimates the hourly output of nitrogen in the urine, it results that the increase during the first seven to ten hours after the milk (compared with the excretion beforehand) amounts only to from 12 per cent to 15 per cent of the nitrogen taken in, while after bread it amounts to 50 per cent. If the hourly rate of absorption and the extent to which milk and bread are respectively used up be taken into consideration, it has to be admitted that these augmentations of urinary nitrogen which appear soon after feeding must be expressions of the functional activity of the digestive canal itself, and that this activity in the case of bread is three or four times greater than in the case of milk {Experiments of Prof. Rjasanzew); consequently, in the case of milk a much larger fraction of its nitrogen is free to be used up by the organism at large (irrespective of the organs of digestion) than in that of any other kind of food. In other words, the price which the organism pays for the nitrogen of milk, in the form of work on the part of its digestive apparatus, is much less than that for other foods.

How admirably, therefore, the food prepared by Nature distinguishes itself when compared with all others!