278 APPENDIX 



gone, yield a negative galvanometric reaction. The 

 negative system of a plant is in the root, stem, stalks, and 

 veins of the leaves. The older the leaves are and as a 

 rule they are those nearest the soil the larger the veins. 

 This argues lower internal resistance, and therefore more 

 current, with, as I have found, greater toxic activity. In 

 all probability only the areolae of the leaves approach 

 chemical neutrality. 



As instances of this we may take the tobacco and tea 

 plants. In the former the lower leaves are coarse- veined, 

 and contain so much essential oil as to be fit only for the 

 manufacture of insecticides, while everyone knows that, 

 given any description of tea, the choicest of it will be the 

 young tips and flowers, owing mainly to their comparative 

 freedom from tannic acid. 



The stalk and veins of the leaves of many plants and 

 vegetables are, no doubt, harmless, but even when Nature 

 does not render them unpalatable instinct teaches us to 

 reject them. If the stalks of the cabbage are not unpleasant 

 of taste they are hard and somewhat fibrous ; so, too, the 

 core of the apple, the white negative substance in the 

 orange, and the root of the lettuce, are bitter, and so on, 

 through a wide range of the vegetable tribes. 



I have no information upon the subject, but venture to 

 express the opinion that vegetable poisons will be found 

 only in those parts of a plant which yield a negative 

 galvanometric deflection. 



In any case it should be of advantage to remove the 

 larger veins by excision from all leaves used for food. The 

 difference in flavour is very marked when this is done, and 

 will more than repay the trouble taken. 



A simple experiment will demonstrate this very 

 effectively. Take, say, | Ib. of any kind of tea. From 

 2 oz. of this pick out and throw away all the loose stalks, 

 of which there are generally many. Then prepare an 



