“Propionic acid 0.0563 Butyric acid 0.0835 Valerianic acid 0.0615 “The quantity digested by a similar liquid containing hydrochloric acid was 0.3376. Hence, taking this as 100, the following numbers represent the relative quantities digested by the other acids:— “Propionic acid 16.5 Butyric acid 24.7 Valerianic acid 16.1 “6. A third experiment of the same kind gave: [page 91] “Quantity of fibrin digested in four hours by 10 cub. cent. of the liquid:— “Hydrochloric acid 0.2915 Propionic acid 0.1490 Butyric acid 0.1044 Valerianic acid 0.0520 “Comparing, as before, the three last numbers with the first taken as 100, the digestive power of propionic acid is represented by 16.8; that of butyric acid by 35.8; and that of valerianic by 17.8. “The mean of these three sets of observations (hydrochloric acid being taken as 100) gives for “Propionic acid 15.8 Butyric acid 32.0 Valerianic acid 21.4 “7. A further experiment was made to ascertain whether the digestive activity of butyric acid (which was selected as being apparently the most efficacious) was relatively greater at ordinary temperatures than at the temperature of the body. It was found that whereas 10 cub. cent. of a liquid containing the ordinary proportion of hydrochloric acid digested 0.1311 gramme, a similar liquid prepared with butyric acid digested 0.0455 gramme of fibrin. “Hence, taking the quantities digested with hydrochloric acid at the temperature of the body as 100, we have the digestive power of hydrochloric acid at the temperature of 16° to 18° Cent. represented by 44.9; that of butyric acid at the same temperature being 15.6.” We here see that at the lower of these two temperatures, hydrochloric acid with pepsin digests, within the same time, rather less than half the quantity of fibrin compared with what it digests at the higher temperature; and the power of butyric acid is reduced in the same proportion under similar conditions and temperatures. We have also seen that butyric acid, which is much more efficacious than propionic or valerianic acids, digests with pepsin at the higher temperature less than a third of the fibrin which is digested at the same temperature by hydrochloric acid.] [page 92] I will now give in detail my experiments on the digestive power of the secretion of Drosera, dividing the substances tried into two series, namely those which are digested more or less completely, and those which are not digested. We shall presently see that all these substances are acted on by the gastric juice of the higher animals in the same manner. I beg leave to call attention to the experiments under the head albumen, showing that the secretion loses its power when neutralised by an alkali, and recovers it when an acid is added. Substances which are completely or partially digested by the Secretion of Drosera.