It is interesting to note the marked purgative effect of pilocarpine in a small fresh-water crustacean (_Sida crystallina_). This animal, which has been spoken of in previous chapters belongs to the Cladocera. The intestine extends in a fairly straight line throughout the body, bending downward at the post abdomen to open to the outside. At the anterior end is a slight dilatation which may represent the stomach. From this there open two diverticula or coeca which seem to be of a glandular nature, and are sometimes spoken of as digestive glands. They are usually filled with a greenish fluid. The intestine is always filled with brown faeces which are normally expelled in small quantities, only at considerable intervals. Slight peristaltic waves are commonly seen in the lower part of the intestine. These animals were placed in various solutions, and it was found[97] that pilocarpine hydrochlorate, aloin, cascara, as well as barium chloride, sodium citrate, sulphate, and fluoride, caused an increased peristaltic activity of the intestine, and a rapid expulsion of faeces, so that in a very short time the entire intestine was empty. At the same time the intestine becomes filled with a greenish fluid similar to that seen in the diverticula. This fluid may be also expelled and replaced again. It is evidently secreted by the intestine or by the diverticula as a result of the purgative action. Very dilute solutions of pilocarpine are sufficient to bring about this effect. In a 1% solution the action is very rapid, and evacuation of faeces may be brought about by a mixture of 1 c.c. 0.1% pilocarpine in 10 c.c. water. This takes place within 20 minutes. An attempt was made to determine whether or not CaCl_{2} is capable of inhibiting the action of pilocarpine. The experiments on rabbits in this respect were unsatisfactory. It was found that the greatest dilution at which expulsion of faeces in Sida could be caused in a short period of time was 1 c.c. 0.1% pilocarpine + 10 c.c. water. Animals were placed in a mixture of 1 c.c. 0.1% pilocarpine + 10 c.c. m/6 CaCl_{2}. These behaved exactly as though the water had not been replaced by CaCl_{2}. In other words, the presence of the CaCl_{2} did not delay at all the action of the pilocarpine. This was repeated many times, and it seems that in Sida at least the action of pilocarpine is not at all antagonized by calcium chloride. In a mixture, however, of 10 c.c. 1% atropin sulphate + 1 c.c. 0.1% pilocarpine no evacuation of faeces took place and there was no increase in peristalsis. FOOTNOTES: [92] MACCALLUM, J. B.: University of California Publications, Physiology, Vol. I, p. 163. [93] Archiv f. exp. Path. u. Pharm., Bd. 43, 1900, S. 274. [94] Schweiz. Wochenschrift für Chemie and Pharmacie, 1898, No. 23. [95] To appear shortly in Journal of Biological Chemistry. [96] _Loc. cit._ [97] MACCALLUM, J. B.: University of California Publications, Vol. II, 1905, p. 65.