May, 1912.] 



425 



Live Stock. 



may apply to the toxicity of some plants 

 is shown by Melter (1899), who records 

 that his horse ate 500 lb. of dried hay 

 of Passiflora incarnata without any 

 injurious effect ; it had been gathered 

 in July when the plant had passed the 

 flowering stage. In the following March, 

 eight months later, the horse ate only 

 25 lb. of the dried plant, which had 

 been gathered for medicinal purposes 

 when in flower (the condition in which 

 it is most potent) ; this time the result 

 was fatal. 



The Condition and Age of a Plant may 

 effect its Toxic Properties. — The poison- 

 ous principle of some plants, e.g., Conium 

 maculatum) is volatile, and the dried 

 material may be less dangerous than the 

 fresh. Hay made from the sleepy grass 

 of New Mexico (Stipa Vaseyi) does not 

 appear to possess any poisonous qualities, 

 although in the fresh state the plant has 

 a narcotic effect on horses (Scribner, 

 1898). The young plants of Lotus ara- 

 bicus of Northern Africa are highly 

 poisonous to horses, sheep, and goats, 

 according to Dunstan and Henry, but 

 the old, mature plants are freely used as 

 a fodder by the natives. Feeding experi- 

 ments with Crotolaria burkenna pro- 

 duced no effect when the plants were 

 partially dried. This factor renders the 

 investigation of the poisonous principle 

 of some plants more difficult, as they 

 lose a large part of the poison on being 

 gathered or prepared for research. 



Some parts of certain plants are more 

 poisonous than others. The fruits of the 

 Hemlock {Conium maculatum) and the 

 seeds of Stramonium {Datura Stramo- 

 nium), of species of Lathyrus, and of 

 other plants contain a larger proportion 

 of poison than the foliage. 



The relative proportion of poison con- 

 tained probably differs in individuals of 

 the same species, just as there is a differ- 

 ence in the flavour or sweetness of two 

 fruits from the same tree, in the amount 

 of latex yielded by different rubber- 

 producing trees of the same species, and 

 in the amount and quality of opium 

 produced by the Opium-poppy under 

 varying conditions of soil and climate. 

 51 



Some kinds of poisonous plants are 

 much more dangerous than others, 

 perhaps because more often eaten, or 

 because the poisonous substance con- 

 tained is more virulent, or because one 

 kind contains a larger proportion than 

 another. Therefore, some species act on 

 the system with great rapidity, while 

 the action of others is relatively slow. 



Small doses of some poisons may be 

 taken with beneficial effect, when large 

 doses may be fatal. Some of the most 

 deadly poisons {e.g., Belladonna, Strych- 

 nine, Aconite) are valuable drugs when 

 taken in official doses. It is evident, 

 thei'efore, that a plant is not necessarily 

 harmless because stock are occasionally 

 seen to eat of it without injurious effect. 



The toxic properties of plants are not 

 of course due in all cases to the same 

 chemical substance. It is well known 

 that several toxic compounds are present 

 in various plants, which differ in their 

 effect on the animal system, e.g., the 

 Alkaloids, nicotine, morphine, atropine, 

 hyoscyamine, strychnine, and veiatine ; 

 the Glucosides, lotusine, coronilline, and 

 amygdaline ; the Gluco-alkaloid solanine; 

 and the Acids aconitic and hydrocyanic. 



Sometimes the same poison is present 

 in more than one species or genus of 

 plants, e.g., hyoscyamine, which is 

 characteristic of the Henbane (Hyoscy- 

 amus niger) and atropine, characteristic 

 of the Deadly nightshade (Atropa Bella- 

 donna), these are both present in the 

 Stramonium (Datura Stramonium) ; sola- 

 nine occurs alike in the Black night- 

 snade (Salanum nigram), the Jerusalem 

 cherry (Solanum pseudocapsicum), the 

 tomato (Lycopersicum esculentum), and 

 in the white sprouts and unripe tubers 

 of the potato (Solanum tuberosum) when 

 grown near the light. 



Similar toxic properties sometimes 

 occur in many plants of the same 

 family. The presence of poisonous alkal- 

 oids, narcotics, acids or acid compounds 

 is often commoa to and characteristic of 

 many species of a genus and even of a 

 family ; thus Hyoscyamus, Atropa, 

 Datura, and Lycopersicum, referred to 



