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Proceedings of the Royal Society of Edinburgh. 
(Continued from Vol. XXXVL., p. 198.) 
Monday, 4th December 1843. 
Sir THOMAS BRISBANE, President, in the Chair. 
The following Communication was read :— 
On the Influence of various Circumstances in Vegetation 
upon the activity of Plants. Part Il. The Umbelli- 
ferous Narcotics. By Dr Christison. 
In the First Part of this inquiry, the author gave an account, in 
1840, of some observations made by him, as to the influence of 
season on the activity of the acrid plants of the natural family 
Ranunculacee, and of the narcotics belonging to the family Dru- 
pacee.* In the Second Part now laid before the Society, he pro- 
ceeded to relate a series of experiments instituted by him with the 
view of determining the influence of season on the activity of the 
poisonous narcotic plants of the family Umbellifere. 
The plants belonging to this family are for the most part aroma- 
tic and stimulant, and destitute of poisonous properties. In four 
species only have narcotic properties been unequivocally recognised, 
viz., Conium maculatum, Cinanthe crocata, Cicuta virosa, and 
Aithusa cynapium ; but these are universally held to be highly 
energetic. 
1. Conium maculatum, Common Hemlock.—No accurate infor- 
mation is yet possessed as to the influence of season on the activity 
of this species : for all investigations on the subject are vitiated by 
the uncertain strength of its preparations, and the ignorance which 
prevailed till very lately as to the conditions required for securing 
their uniformity. The author has found by experiment, as Profes- 
sor Geiger had already been led to conclude, that every part of the 
plant is poisonous, both the root, the leaves, and the fruit ; and that 
the root is least active, the leaves much more so, but the fruit the 
most active of all. The root is commonly held to be most active in 
midsummer, when the plant is in full vegetation and coming into 
flower ; but this belief is founded only on a single, and not alto- 
gether conclusive, experiment made by Professor Orjila. This 
author found this part of the plant to be so feeble at all times, that 
its respective energy at different seasons could not be satisfactorily 
settled. The expressed juice of twelve ounces of roots had no ap- 
preciable effect on a small dog in the end of October or towards the 
* See the Society’s Proceedings, 1840-41. 
