MEDICO-LEGAL CONTRIBUTIONS ON ARSENIC. 
171 
supposed to have been found in the body. In England the 
celebrated Palmer case offers an instance to the contrary, 
and others might be mentioned. There seems to be no good 
reason (where other evidence is positive) why a conviction 
should not be obtained, even in the absence of chemical 
evidence; all that is necessary in such a case is to satisfy 
the jury that the deceased died from poison, and this occa¬ 
sionally may be done without, as well as with, the class of 
evidence we are speaking of. 
' The detection of poisons in the tissues generally, as well 
as in the intestinal tract, and in the food and medicine given, 
furnishes the most complete chemical evidence of poisoning; 
if only found in the stomach or in the food or medicine, the 
testimony is weakened, because there is a possibility that it 
might have been placed there subsequently. 
There are certain fallacies which must be guarded against 
in receiving evidence derived from chemical examinations in 
medico-legal investigations. It is not to be supposed that 
in all cases such examinations will be made b}^ those most 
competent, and hence, besides the inherent difficulties of 
such researches, it is necessary to ensure ourselves against 
the ignorance and unskilfulness of the operator. Thus we 
mav allude to the meagreness or absence of characteristic 
tests for many organic poisons, and the difficulty of separat¬ 
ing them from organic mixtures. Again, and this is more 
pertinent to the subject of this paper, it has been ascertained 
that many of the reagents, supposed to be pure, are often 
contaminated with poisons. 
Thus, arsenic is often found in zinc, sulphuric acid, and 
chlorhydric acid, and in other materials used in toxical 
investigations. The knowledge of this fact causes us to 
doubt whether the arsenic discovered in minute quantities in 
many reported cases was contained in the remains examined 
or in the chemicals used. The above remarks illustrate the 
great danger there is in relying upon the supposed detection 
of minute quantities of poison, in the absence of physio¬ 
logical and pathological evidence, and without a careful 
examination by competent authority of the methods followed 
in operating upon the materials examined. 
Before treating of the methods of analysis, a few remarks 
may be made concerning the— 
2. Physical Examination of Materials for Analysis. — Food, 
Contents of the Stomach, Syc .—By a careful examination of these 
substances, poison may often be discovered. The best mode 
of procedure is to place a part of the suspected mass into a 
glass vessel, such as a beaker, and, after adding water, stir 
