664 POISONS : THEIR EFFECTS AND DETECTION. [§ 844 . 
line round the gums, but describes it as purple-red. Among workers in 
copper, Lancereaux 1 has seen a black coloration of the mucous mem¬ 
brane of the digestive canal ; its chemical characters appear to agree 
with those of carbon. 
Metallic copper itself is not poisonous. A Mr Charles Reed has 
published a letter in the Chemical News of January 12, 1894, stating that 
he was, when a boy, wounded in the shin by a copper percussion-cap, 
and the cap remained in the tissues ; it was removed from the shin 
after a sojourn there of some twelve years ; about the year 1873 he 
noticed that whenever a piece' of clean iron or steel came in contact with 
his perspiration it was at once covered with a bright coating of copper, 
and this continued until the percussion-cap was removed. Presuming 
the truth of this, it shows conclusively that metallic copper deposited in 
the tissues is in itself not poisonous, and further, that one method of 
elimination is by the skin. The experiments already cited throw doubt 
as to whether repeated small doses of copper taken for a long time 
produce, in a scientific sense, chronic poisoning ; those which apparently 
support the view that there is such a thing as chronic poisoning by 
copper have been produced by copper mixed with other metals, and 
there is the possibility that these cases are really due to lead or arsenic 
and not to copper. The great use of late years of solutions of copper 
sulphate as a dressing to plants, for the purpose of preventing the 
ravages of various parasites, has provided, so far as animals are concerned, 
much material for the judgment of this question. Sheep have been fed 
with vines which have been treated with copper sulphate, oxen and pigs 
have consumed for a long time grass treated with a *3 per cent, solution 
of copper sulphate, without the least health disturbance. Mach 2 has 
fed cows with green food coppered up to 200 mgrms. of copper sulphate, 
without observing the slightest bad effect, for long periods of time ; and 
Tschirch 3 summarises the evidence as to chronic poisoning as follows :— 
“ So it appears the contention that there is no chronic poisoning in men 
or animals is at present uncontradicted ; it is further to be considered 
proved that the small amounts of copper naturally in food, or carefully 
introduced into food, are not injurious to the health of those that take 
such food, because the liver, kidneys, and other organs excrete the 
copper through the urine and bile, and prevent a pernicious accumu¬ 
lation.” At the same time, Tschirch does not consider the question is 
definitely settled ; the experiments should, he thinks, have been con¬ 
tinued not for months, but for years, to obtain a trustworthy judgment. 
It may also be remarked that, if we are to rely upon the separation 
of copper by the kidneys and the liver, those organs are presumed to be 
1 Atlas of Pathological. Anatomy. 
2 Mach, Bericht iiber die Ergebnisse der im Jahre 1886 ausgefiihrten Versuche zur 
Bekampfung der Peronospora, St Michele, Tyrol. 3 Op. cit. 
