Poison from the Cobra.—Dr. Fayrer, well known from his investigations on the poison of this deadly snake, was so kind as to give me some in a dried state. It is an albuminous substance, and is believed to replace the ptyaline of saliva.* A minute drop (about 1/20 of a minim) of a solution of one part to 437 of water was applied to the secretion round four glands; so that each received only about 1/38400 of a grain (.0016 mg.). The operation was repeated on four other glands; and in 15 m. several of the eight tentacles became well inflected, and all of them in 2 hrs. Next morning, after 24 hrs., they were still inflected, and the glands of a very pale pink colour. After an additional 24 hrs. they were nearly re-expanded, and completely so on the succeeding day; but most of the glands remained almost white.
Half-minims of the same solution were placed on the discs of three leaves, so that each received 1/960 of a grain (.0675 mg.); in
*Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 150. [page 207]
4 hrs. 15 m. the outer tentacles were much inflected; and after 6 hrs. 30 m. those on two of the leaves were closely inflected and the blade of one; the third leaf was only moderately affected. The leaves remained in the same state during the next day, but after 48 hrs. re-expanded.
Three leaves were now immersed, each in thirty minims of the solution, so that each received 1/16 of a grain, or 4.048 mg. In 6 m. there was some inflection, which steadily increased, so that after 2 hrs. 30 m. all three leaves were closely inflected; the glands were at first somewhat darkened, then rendered pale; and the protoplasm within the cells of the tentacles was partially aggregated. The little masses of protoplasm were examined after 3 hrs., and again after 7 hrs., and on no other occasion have I seen them undergoing such rapid changes of form. After 8 hrs. 30 m. the glands had become quite white; they had not secreted any great quantity of mucus. The leaves were now placed in water, and after 40 hrs. re-expanded, showing that they were not much or at all injured. During their immersion in water the protoplasm within the cells of the tentacles was occasionally examined, and always found in strong movement.
Two leaves were next immersed, each in thirty minims of a much stronger solution, of one part to 109 of water; so that each received 1/4 of a grain, or 16.2 mg; After 1 hr. 45 m. the sub-marginal tentacles were strongly inflected, with the glands somewhat pale; after 3 hrs. 30 m. both leaves had all their tentacles closely inflected and the glands white. Hence the weaker solution, as in so many other cases, induced more rapid inflection than the stronger one; but the glands were sooner rendered white by the latter. After an immersion of 24 hrs. some of the tentacles were examined, and the protoplasm, still of a fine purple colour, was found aggregated into chains of small globular masses. These changed their shapes with remarkable quickness. After an immersion of 48 hrs. they were again examined, and their movements were so plain that they could easily be seen under a weak power. The leaves were now placed in water, and after 24 hrs. (i.e. 72 hrs. from their first immersion) the little masses of protoplasm, which had become of a dingy purple, were still in strong movement, changing their shapes, coalescing, and again separating.
In 8 hrs. after these two leaves had been placed in water (i.e. in 56 hrs. after their immersion in the solution) they began to re-expand, and by the next morning were more expanded. After an additional day (i.e. on the fourth day after their immersion in the solution) they were largely, but not quite fully [page 208] expanded. The tentacles were now examined, and the aggregated masses were almost wholly redissolved; the cells being filled with homogeneous purple fluid, with the exception here and there of a single globular mass. We thus see how completely the protoplasm had escaped all injury from the poison. As the glands were soon rendered quite white, it occurred to me that their texture might have been modified in such a manner as to prevent the poison passing into the cells beneath, and consequently that the protoplasm within these cells had not been at all affected. Accordingly I placed another leaf, which had been immersed for 48 hrs. in the poison and afterwards for 24 hrs. in water, in a little solution of one part of carbonate of ammonia to 218 of water; in 30 m. the protoplasm in the cells beneath the glands became darker, and in the course of 24 hrs. the tentacles were filled down to their bases with dark-coloured spherical masses. Hence the glands had not lost their power of absorption, as far as the carbonate of ammonia is concerned.
From these facts it is manifest that the poison of the cobra, though so deadly to animals, is not at all poisonous to Drosera; yet it causes strong and rapid inflection of the tentacles, and soon discharges all colour from the glands. It seems even to act as a stimulant to the protoplasm, for after considerable experience in observing the movements of this substance in Drosera, I have never seen it on any other occasion in so active a state. I was therefore anxious to learn how this poison affected animal protoplasm; and Dr. Fayrer was so kind as to make some observations for me, which he has since published.* Ciliated epithelium from the mouth of a frog was placed in a solution of .03 gramme to 4.6 cubic cm. of water; others being placed at the same time in pure water for comparison. The movements of the cilia in the solution seemed at first increased, but soon languished, and after between 15 and 20 minutes ceased; whilst those in the water were still acting vigorously. The white corpuscles of the blood of a frog, and the cilia on two infusorial animals, a Paramaecium and Volvox, were similarly affected by the poison. Dr. Fayrer also found that the muscle of a frog lost its irritability after an immersion of 20 m. in the solution, not then responding to a strong electrical current. On the other hand, the movements of the cilia on the mantle of an Unio were not always arrested, even when left for a consider-
* ‘Proceedings of Royal Society,’ Feb. 18, 1875. [page 209]
able time in a very strong solution. On the whole, it seems that the poison of the cobra acts far more injuriously on the protoplasm of the higher animals than on that of Drosera.