160 ^lEDICINAL HERBS AND POISOXOUS PLANTS 



stalk. They are thick, coriaceous, dark -green, smooth, 

 liaving a shining upper surface: on the under side the 

 colour is of a paler hue (fig. 101). Near the base are 

 one or two glandular depressions. Wlien bruised the 

 leaves give out an odour resembling that of bitter 

 almonds. Laurel leaves are used with great success for 

 flavouring custards; but it must be noted, first, that the 

 very vapour arising from them is destructive to insect 

 life, and secondly, laurel -water is a very poisonous 

 liquid. In the case of this plant the potentially dan- 

 gerous substance is not amygdalin, but a closely allied 

 glucoside called lauro-cerasin, which also changes into 

 prussie acid by the intervention of the appropriate fer- 

 ment. The preparation called Aqua Lauro-cerasi is 

 made from the fresh leaves of the Laurel, and contains 

 1 to 10 per cent prussie acid. The danger arises from 

 the fact that there can be no absolute certainty of the 

 amount of change into prussie acid that may have taken 

 place in the lauro-cerasin of any part of the Laurel that 

 is being used. There is said to be more prussie acid in 

 leaves gathered in cold and wet weather than in those 

 picked when the weather is hot and dry. Again, the 

 Continental species of Laurel yields more prussie acid 

 than the British plant. 



Whilst laurel- water is decidedly poisonous, and whilst 

 there ai-e records against the leaves from the Continent 

 as having caused the death of sheep and oxen, we have 

 to state that Henslow mentions the fact that his cows 

 ruined a long laurel hedge without any ill effects to 

 themselves. This only serves to emphasize the variable 

 nature in the occurrence of the poison in this plant. 



Medicinal uses. — The principal use for cherry-laurel 

 water is for flavouring; it is also used as a sedative, 

 prussie acid in very small quantities producing this effect 

 on the human system. 



