142 VETEEINARY TOXICOLOGY 



0"1 to 0'18 per cent, of taxine. It seems likely, further, 

 that the leaves of the male contain slightly more alkaloid 

 than those of the female tree, but the difference is 

 trifling. 



Much controversy formerly existed as to the poisonous 

 effects of yew, it having been held that the poisonous 

 qualities vary with the season, with the freshness of the 

 leaves, and with the species of the animal. But there can 

 no longer be any doubt that the leaves at all times may be 

 poisonous. The alkaloid may be easily separated and detected 

 from dried or undried leaves. Well-authenticated examples 

 of poisoning among the domesticated animals are very 

 numerous, and the definite toxicity of the alkaloid extracted 

 chemically from the leaves may be readily observed upon 

 experimental animals. Such variations as have been ob- 

 served are readily comprehensible in consideration of the 

 known variability in the action of any poison according to 

 the condition of the alimentary system and individuality 

 of the subject. When a few sprigs of yew are eaten by an 

 animal on a full stomach, it is quite to be expected that 

 dangerous results may not ensue. 



Action and Toxic Doses. — The action of yew, as of so 

 many plants, is twofold. The sap is acrid, containing a 

 volatile oil, or oil of yew, and the plant therefore produces 

 irritation. The specific poison, or taxine, is non-irritant. 

 It acts as a narcotic, producing, according to Borchero 

 (1876), depression of the heart, paralysis of the respiratory 

 functions, and death by suffocation. It has been alleged 

 that the guinea-pig is not susceptible.' 



According to Cornevin,* the poisonous doses are — 



Grains per 1 Pdlmd 

 Bgdy Weight. 



Horse ... ... ... ... ... 15 



Ox 



Sheep 



Goat 



Pig 



75 

 75 

 90 

 22 



* Cornevin, ' Des Plantes Vto^neuses.' 



