POISONOUS PLANTS 193 



small, ovate, and pointed. Pedicles from the upper axils or 

 forks of the stem, 2 or 3 lines long, and slender. Sepals 

 pointed, about IJ lines long. Petals usually much shorter, 

 but variable in size, obovate. Capsule opening in six. 

 narrow valves.'* 



StellaFia.— This genus (the star-worts), represented by 

 several British species, was noted by Cobboldt as being 

 responsible for the poisoning of horses in Russia, and as 

 having occasioned losses in the Crimea campaign. 



Active Ppinciple. — All these plants owe their poisonous- 

 properties to glucosides of the saponin type, which are 

 widely diffused in the plant kingdom, and which present 

 minor differences to one another. The officinal Quillaja 

 Saponaria (Eosacese) is a chief source of saponin. It is 

 native to South America, and is known as Chili soap 

 bark, or Panama root. The saponins possess certain 

 interesting properties which throw light on their physio- 

 logical effects. They do not form true solutions in water, 

 but give colloid suspensions, and impart remarkable , 

 and permanent frothing qualities to the liquid. For this 

 reason saponin is used as an adulterant to such beverages 

 as lemonade. The saponins are not diffusible, being 

 colloidal, and are therefore not easily absorbed. When 

 taken by the mouth it is probable that absorption only 

 occurs when inflammatory lesions are also caused, as 

 happens with some of the plants. When introduced into 

 the blood stream the saponins cause haemolysis, or dissolu- 

 tion of the red cells, and also similarly act on other cells — 

 e.g., of ganglia. To these effects are due the nervous 

 symptoms of stupefaction and paralysis. Saponin is taken 

 up from water by the gills of fishes into the blood stream, and 

 thus produces poisoning, even in a dilution of 1 to 200,000.. 

 The hsemolytic action is stopped by cholesterol, which thus 

 directly neutralises or antagonises saponin poisoning. 



It has been stated that animals develop tolerance (or 

 immunity ?) after continual feeding on small doses of corn- 

 cockle meal. 



* Bentham and Hooker. f Veterinarian, 1880, p. 453. 



13 



