In considering these results it must be remembered that the soil is naturally suited to the plant, and the percentage of alkaloid obtained without added fertilisers is already high. The low figures obtained in 1907 were probably due to the seasonal conditions. Atmospheric conditions have a modifying influence.
It was also shown that the Belladonna root of commerce varies greatly in alkaloid strength. “In a number of analyses made of commercial roots, variations from 0·27 to 0·69 per cent. have occurred. The average of twenty-one analyses of German and Austrian commercial roots was 0·40 per cent. Other observers have recorded similar results. Chevalier (Compt. Rend., 1910, 150, 344) gives the following figures for Continental roots: French, 0·300 to 0·450 per cent.; Austrian, 0·251 to 0·372 per cent.; Italian, 0·107 to 0·187 per cent. Henderson has shown the average of thirty samples of foreign root to be 0·3 per cent. It is interesting to observe that the average of nine samples of root grown at Darenth is 0·54 per cent. In order to determine whether this variation was due to collecting at different times of the year, roots from the same plot, derived from second year’s plants, which were sown at the same time, were dug up at intervals and dried. The following is a record of the analysis of these samples:—
| March, 1911 | 0·56 | per cent. |
| May, 1911 | 0·59 | „ „ |
| June, 1911 | 0·53 | „ „ |
| August, 1911 | 0·50 | „ „ |
| December, 1911 | 0·59 | „ „ |
“The amount of variation throughout the year is thus seen to be very small.”
Dunstan (Bul. Imp. Inst., 1905) has shown that Hyoscyamus muticus grown in India yielded 0·3 to 0·4 per cent. of hyoscyamine, but that the same species grown in Egypt produced 0·6 to 1·2 per cent.
According to Esser no coniine is found in Conium maculatum growing in the far north. The same authority says that the root of Hyoscyamus niger is quite free from toxic properties in winter.
Variation in the Poisonous Parts of Plants. As will be shown in succeeding chapters, many plants (e.g. meadow saffron) are poisonous in all their parts, though the amount of the toxic substance may differ according as to whether the seeds, leaves, stem or roots are severally considered. In other cases one part of the plant alone is toxic (e.g. the seeds, as in corn cockle). Further, some species vary in the percentage of the toxic substance in the leaves before and after flowering. Frequently the root is the most toxic portion of the plant. This point may be usefully recollected in relation to poisoning of live stock, which are in general affected by the foliage or ripe seeds.
Eradication of Poisonous Plants. Wherever poisonous plants are found, particularly in quantity, where they are liable to be eaten by live stock, an attempt should be made to eradicate them. They may be simply dealt with as weeds as may be necessary according to the species concerned. When any difficulty is experienced in regard either to determination of the species or to methods of eradication the advice of the Board of Agriculture and Fisheries (Whitehall Place, London, S.W.) should be requested. Stock should at once be removed from a suspected pasture, which should be immediately and thoroughly examined by a competent botanist. Harmful plants should be eradicated and their place filled by better herbage.
Treatment of Poisoned Animals. This volume makes no pretensions to deal with the veterinary treatment of cases of plant poisoning. Whenever poisoning is suspected the services of a veterinary surgeon should be sought without delay; the text books at his disposal will aid him in the treatment of any case which presents unusual difficulties. The symptoms indicated in the following pages, together with the possible discovery of a suspected plant, may be utilised in diagnosis.
Tests with Suspected Plants. The action of plants on animals may be ascertained (1) by observing the effects in cases in which it has been established that the plants have been eaten, or (2) by direct experimental feeding of animals with the plant. In the first case the results may be accurate and satisfactory if observations have been made from the outset.