1888.] Toxic Principle of the Aroide^. 117 



the stomach, it would be acted upon by the gastric juice containing free 

 hydrochloric acid, — and that acid, as is well-known, is a ready solvent for 

 calcic oxalate, — so that, before the vegetable matter containing the needle- 

 shaped crystals could enter the intestine, it would have lost its mechani- 

 cal irritative properties. In answer to this we would merely remark, that, 

 when mechanical irritation of the stomach is carried beyond certain 

 limits, so as to produce pain, the secretion of the gastric juice, instead of 

 becoming more abundant, diminishes or ceases entirely, and a ropy mucus 

 is poured out instead.* And it also appears likely to us that the great 

 irritation produced in the mouth would react upon the stomach ; for, 

 according to experiments by M. Blondlot, the quantity of the secretion 

 seems to be influenced also by impressions made on the mouth. t We 

 thus fail to see any reason why the arum tissues loaded with needle- 

 shaped crystals should not enter the intestines. Once in the intestines, 

 the mechanical effects of the crystals would be to induce convulsions, 

 dilated pupils, and coma ; all of which symptoms are often caused by the 

 mechanical irritation of intestinal worms. 



This theory of the mechanical action of the arums, which we 

 advanced in 1886, has since, apparently, been independently adopted by 

 Herr Stahl, who, at a recent meeting of the Jena Naturalists' Society, 

 read a paper on the significance of those excreta of plants which are 

 known as raphides, and are so often met with in the cells in large quantity. 

 From experiments this investigator inferred that they were a protection 

 to plants against being eaten by animals. Many animals avoid plants with 

 raphides, or eat them reluctantly ; and some animals, e. g., snail species, in 

 eating plants that have raphides, select those parts that are without the 

 crystals. Many plants held for poisonous, e. g., Arum maculatum^ owe 

 their burning taste simply to the very numerous raphides, which, forced 

 out of their cells, enter the tongue and palate. The juice obtained by 

 filtration has quite a mild taste.;]: 



* Kirke's Physiology. 



t lUd. 



X " Nature," Dec. 29th, 1887. 



