THE POISONOUS PLANTS OF BOMBAY. 57 



bility of calcic oxalate in these mineral acids. This was verified in 

 every instance under the microscope. Warden and Pedler found that, 

 on drying, the tubers practically lost the whole of their physiological 

 activity. " Clearly," they say, " there could have been no loss of 

 oxalate of lime on desiccation ; " and as a matter of fact they found 

 as many crystals under the microscope in the dried arum as in the 

 fresh tubers. They admit however that this is an anomaly and explain 

 it as follows : — " In the fresh condition of the tubers, the bundles of 

 crystals of oxalate of lime are cone-shaped more or less, the sharp 

 points covering a wide area and forming the base, but in the 

 drying of the tubers the needles appear to arrange themselves more 

 or less parallel to one another, and the sharp points thus cover a small 

 area. And thus, instead of each crystal acting as a separate source 

 of irritation and penetrating the tissues, the bundles act as a whole." 



In the Pharmacographia Indica (vol. Ill, p. 547) needle-shaped . 

 crystals are mentioned by Dr. Dymock as forming the contents of 

 the cells composing the parenchyma of the fruit and seed of Syrian- 

 therias sylvatica, Schott. 



The mechanical theory of irritation by the pointed ends of the 

 crystals, say Warden and Pedler, has been independently adopted by 

 Herr Stahl of Jena. They admit, however, that, in addition to local 

 irritation, viz., of the tongue, throat, and mouth, there are other and 

 graver symptoms produced by the ingestion of arum-tubers and leaves, 

 such as convulsions, dilated pupils, insensibility and coma, and that 

 the occurrence of these symptoms cannot be explained by the mecha- 

 nical theory. They look upon these symptoms as the result of the 

 action of the calcic oxalate crystals on the stomach. They say that the 

 stomach at first suffers from mechanical irritation by the crystals ; the 

 secretion of the gastric juice thereby diminishes or ceases entirely ; 

 free hydrochloric acid of the gastric juice is, in consequence, not 

 ' available for dissolving the calcic oxalate crystals ; the crystals thus 

 may pass on to the intestinal canal ; once in the intestines, they may 

 induce convulsions, dilated pupils, and coma by mechanical irritation 

 in the^ same manner as intestinal worms. 



Believing that the irritation caused by the tubers of Suran is due 

 to the mechanical action of the needle-shaped crystals found in their 

 cells in close-packed bundles, I have thus freely and fully reproduced, 

 although in the form of a summary, the exhaustive researches of 

 Warden and Pedler. The importance of their results will be amply 



