94 Scientific Proceedings, Royal Dublin Society. 



from 150 grammes of leaves gathered on January 17th, 1909, weighed only 

 0-1236 gramme, corresponding to 0'082 per cent. This is less than half tlio 

 quantity found by Thorpe and Stubbs in the leaves they examined. 



I believe these estimations are fairly comparable witli one another, and 

 that they may be accepted as showing a wide variation in the quantity of 

 alkaloidal substance in the leaves of different trees. Carnevin' points out 

 that the young leaves of a light green colour are not nearly so poisonous as 

 the older dark green leaves ; accordingly I took some trouble to ensure that 

 the leaves gathered fairly represented the foliage of each tree, and did not 

 include an undue proportion of either old or young leaves. The number of 

 determinations is too small to warrant the final conclusion that the variety 

 known as Irish Tew contains much more taxine than common Yew, but that 

 is certainly the direction in which the results point. This is quite in accor- 

 dance with an opinion which I find has long been entertained. For example, 

 in the Pharmaceutical Journal of 1877,' there is a reference to letters in the 

 Field (I have been unable to find the originals in that journal), in one of 

 which a correspondent states that in the case of pheasants poisoned by Yew 

 he has observed that the leaves found in the crops and gizzards of the birds 

 are always Irish Yew ; and he believes they may eat common Yew with 

 impunity. 



The very marked variation in the quantity of alkaloidal substance in the 

 leaves of the plants also explains in some degree the widely different opinions 

 expressed from time to time as to the toxic properties of Yew. 



I have not had an opportunity of examining the seeds of common Yew ; 

 but from the similarity of the results obtained with the seeds of different 

 specimens of Irish Yew it seems probable that the alkaloidal substance is 

 more constant in quantity in the seeds than in the leaves. Many of the 

 recorded cases of poisoning by the seeds of Yew are presumably attributable 

 to the Irish variety, as the trees are referred to as growing in cemeteries, and 

 it has long been the custom to plant the Irish Yew in such places. 



I have assumed that the alkaloidal substance referred to is the toxic 

 principle of the Yew; but it is right to point out that this is by no means 

 certain. Experimental work in this connexion is very desirable. 



Taxine and its compounds are non-crystalline ; and they exhibit no 

 distinctive reaction. It is therefore not easy to ensure that the alkaloidal 

 substance obtained from different sources is the same thing. 



The melting-point of taxine is not clearly marked. I find that wlien the 

 solid obtained by evaporating the ethereal solution of taxine, and drying in 



1 " Dea Plantes Veneneuses et des Empoiaoanements qu'elles determinent," p. 48. 



2 Ser. 3, vol. vii., p. 697. 



