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PROFESSOR W. N. HARTLEY OH THE 
can be placed upon the mere appearance of crystals; they must be submitted to 
recrystallisation by sublimation or some other process. The physiological action of 
certain alkaloids of an extremely deadly character is remarkable enough to prove a 
means of identifying the substance when the effect on the human subject is under 
observation ; but it is to some extent capable of being modified by the extent of the 
dose, the administration of other drugs, or the idiosyncracy of the patient. These 
facts are well known, and are generally made use of by the counsel for the defence in 
medico-legal cases. When the identification of an alkaloid is a necessary part of the 
evidence of the administration of poison, experiments of a physiological character have 
necessarily to be made on the lower animals. It has been objected that the action of 
drugs on creatures of a smaller size and different organisation may be, and, in certain 
cases, indeed is, unlike that produced in the human organism, and comparative experi¬ 
ments are necessary in which the suspected substance is compared with authentic 
specimens before its identity can be established. But in such comparative experi¬ 
ments an element of uncertainty is introduced, because various preparations supposed 
to be the same alkaloid may differ in physiological action to such an extent that 
reasonable doubts may be entertained as to whether they consist of the same substance 
or, indeed, of one substance only. The whole subject of the modification of alkaloids 
by the reagents used in their extraction, variations in their crystalline character and 
in their physiological action, can be well illustrated by reference, to the. researches of 
Dr. C. R. A. Wright on the various preparations known as aconitine.- 
The evidence given at the trial of George Henry Lamson, a surgeon, at the 
Central Criminal Court in 1882, for poisoning with aconitine, conferred greatly 
increased importance upon any method of absolute physical measurement which might 
be substituted for the ordinary tests in the identification of the dangerous alkaloids. 
Almost all active alkaloids have a complex chemical constitution, and every complex 
molecule in which carbon is in a certain state of condensation has a definite absorption 
spectrum in the ultra-violet if not in the visible region. In most cases the absorption 
curve is peculiar and often strikingly characteristic, and only minute quantities of 
material are actually required for obtaining measurements of spectra from which such 
curves may be plotted. The interest that attaches to an examination of the absorption 
spectra of the alkaloids is not alone the fact that a means of recognising, detecting, 
and estimating, such substances may be devised, but still more that we may learn 
something of their chemical constitution. 
The experimental details. 
The method of examination employed was that described in the Phil. Trans., 
Yol. 170, p. 257, 1879, but the spectroscope was the short focussed instrument 
employed for photographing the spectra published in the ‘Journal of the Chemical 
Society,’ vol. xli., p. 84. 
