dency; in these two latter cases the surrounding fluid was not coloured pink, and the leaves were not poisoned. On the other hand, propionic acid, which is poisonous, does not cause much mucus to be secreted, yet the surrounding fluid became slightly pink. Lastly, as in the case of saline solutions, leaves, after being immersed in certain acids, were soon acted on by phosphate of ammonia; on the other hand, they were not thus affected after immersion in certain other acids. To this subject, however, I shall have to recur. [page 199] CHAPTER IX. THE EFFECTS OF CERTAIN ALKALOID POISONS, OTHER SUBSTANCES AND VAPOURS. Strychnine, salts of—Quinine, sulphate of, does not soon arrest the movement of the protoplasm—Other salts of quinine—Digitaline—Nicotine—Atropine—Veratrine— Colchicine— Theine—Curare—Morphia—Hyoscyamus—Poison of the cobra, apparently accelerates the movements of the protoplasm—Camphor, a powerful stimulant, its vapour narcotic—Certain essential oils excite movement—Glycerine—Water and certain solutions retard or prevent the subsequent action of phosphate of ammonia—Alcohol innocuous, its vapour narcotic and poisonous—Chloroform, sulphuric and nitric ether, their stimulant, poisonous, and narcotic power—Carbonic acid narcotic, not quickly poisonous—Concluding remarks. As in the last chapter, I will first give my experiments, and then a brief summary of the results with some concluding remarks. [Acetate of Strychnine.—Half-minims of a solution of one part to 437 of water were placed on the discs of six leaves; so that each received 1/960 of a grain, or .0675 mg. In 2 hrs. 30 m. the outer tentacles on some of them were inflected, but in an irregular manner, sometimes only on one side of the leaf. The next morning, after 22 hrs. 30 m. the inflection had not increased. The glands on the central disc were blackened, and had ceased secreting. After an additional 24 hrs. all the central glands seemed dead, but the inflected tentacles had re-expanded and appeared quite healthy. Hence the poisonous action of strychnine seems confined to the glands which have absorbed it; nevertheless, these glands transmit a motor impulse to the exterior tentacles. Minute drops (about 1/20 of a minim) of the same solution applied to the glands of the outer tentacles occasionally caused them to bend. The poison does not seem to act quickly, for having applied to several glands similar drops of a rather stronger solution, of one part to 292 of water, this did not prevent the tentacles bending, when their glands [page 200] were excited, after an interval of a quarter to three quarters of an hour, by being rubbed or given bits of meat. Similar drops of a solution of one part to 218 of water (2 grs. to 1 oz.) quickly blackened the glands; some few tentacles thus treated moved, whilst others did not. The latter, however, on being subsequently moistened with saliva or given bits of meat, became incurved, though