round the margins of the discs were a little inflected, and the secretion collected on the disc was acid, but the exterior tentacles were not affected.  One leaf began to re-expand on the fourth day, and all were fully re-expanded on the sixth.  The glands which had been in contact with the mucin were a little darkened.  We may therefore conclude that a small amount of some impurity of a moderately exciting nature had been absorbed.  That the mucin employed by me did contain some soluble matter was proved by Dr. Sanderson, who on subjecting it to artificial gastric juice found that in 1 hr. some was dissolved, but only in the proportion of 23 to 100 of fibrin during the same time.  The cubes, though perhaps rather softer than those left in water for the same time, retained their angles as sharp as ever.  We may therefore infer that the mucin itself was not dissolved or digested.  Nor is it digested by the gastric juice of living animals, and according to Schiff* it is a layer of this substance which protects the coats of the stomach from being corroded during digestion.

Pepsin.—­My experiments are hardly worth giving, as it is scarcely possible to prepare pepsin free from other albuminoids; but I was curious to ascertain, as far as that was possible, whether the ferment of the secretion of Drosera would act on the ferment of the gastric juice of animals.  I first used the common pepsin sold for medicinal purposes, and afterwards some which was much purer, prepared for me by Dr. Moore.  Five leaves to which a considerable quantity of the former was given remained inflected for five days; four of them then died, apparently from too great stimulation.  I then tried Dr. Moore’s pepsin, making it into a paste with water, and placing such small particles on the discs of five leaves that all would have been quickly dissolved had it been meat or albumen.  The leaves were soon inflected; two of them began to re-expand after only 20 hrs., and the other three were almost completely re-expanded after 44 hrs.  Some of the glands which had been in contact with the particles of pepsin, or with the acid secretion surrounding them, were singularly pale, whereas others were singularly dark-coloured.  Some of the secretion was scraped off and examined under a high power; and it abounded with granules undistinguishable from those of pepsin left in water for the same length of time.  We may therefore infer, as highly probable (remembering what small quantities were given), that the ferment of Drosera does not act on or digest

* ‘Leons phys. de la Digestion,’ 1867, tom. ii., p. 304. [page 124]

pepsin, but absorbs from it some albuminous impurity which induces inflection, and which in large quantity is highly injurious.  Dr. Lauder Brunton at my request endeavoured to ascertain whether pepsin with hydrochloric acid would digest pepsin, and as far as he could judge, it had no such power.  Gastric juice, therefore, apparently agrees in this respect with the secretion of Drosera.