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Show 118 DROSERA ROTUNDIFOLIA. CHAP. VI. Smaller bits were placed on two leaves; these were only slightly inflected in t~o days, . but afterwards became much more so. Then secretion was not so strongly acid as that of leaves excited by casein. The bits of gluten, after lying for three days on the leaves, were more transparent than other bits left for the same time in water. After seven days both loaves re-expanded, but the gluten seemed hardly at all reduced in bulk. The glands which had been in contact with it were extremely black. Still smaller bits of half putrid gluten were now tried on two leaves; these were well inflected in 24 hrs., and thoroughly in four days, the glands in contact being 1nuch blackened. After five days one leaf began to re-expand, and after eight days both were fully reexpanded, some glvten being still left on their discs. Four little chips of dried gluten, just dipped in water, were next tried, and these acted rather differently from fresh gluten. One leaf was almost fully re-expanded in three days, and the other three leaves in four days. The chips were greatly softened, almost liquefied, but not nearly all dissolved. The glands which had been in contact with them, instead of being much blackened, were of a very pale colour, and many of them were evidently killed. In not one of these, ten cases was the whole of the gluten dissolved, even when very small bits were given. I therefore asked Dr. Burdon Sanderson to try gluten in artificial digestive fluid of pepsin with hydrochloric acid ; and this dissolved the whole. The gluten, however, was acted on much more slowly than fibrin ; the proportion dissolved within four hours being as 40·8 of gluten to 100 of fibrin. Gluten was also tried in two other digestive fluids, in which hydrochloric acid ·was replaced by propionic CHAP. VI. DIGESTION. 119 and butyric acids, and it was completely dissolved by these fluids at the ordinary temperature of a room. Here, then, at last, we have a case in which it appears that there exists an essential difference in digestive power between the secretion of Drosera and gastric juice; the difference being confined to the ferment, for, as we have just seen, pepsin in combination with acids of the acetic series acts perfectly on gluten. I believe that the explanation lies simply in the fact that gluten is too powerful a stimulant (like raw meat, or phosphate of lime, or even too large a piece of albumen), and that it injures or kills the glands before they have had time to pour forth a sufficient supply of the proper secretion. That some matter is absorbed from the gluten, we have clear evidence in the length of time during which the tentacles remain inflected, and in the greatly changed colour of the glands. At the suggestion of Dr. Sanderson, some gluten was left for 15 hrs. in weak hydrochloric acid ( ·02 per cent.), in order to remove the starch. It became colourless, more transparent, and swollen. Small portions were washed and placed on five leaves, which were soon closely inflected, but to my surprise reexpanded completely in 48 hrs. A mere vestige of gluten was left on two of the leaves, and not a vestige on the other three. The viscid and acid secretion, which remained on the discs of the three latter leaves, was sera ped off and examined by my son under a high power; but nothing could be seen except a little dirt, and a good many starch grains which had not been dissolved by the hydrochloric acid. Some of the glands were rather pale. We· thus learn that gluten, treated with weak hydrochloric acid, is not so powerful or so enduring a |