This comes from continuous injudicious dosing with arsenic, or from the
condensing on the grass of the vapors from the smelting of ores
containing arsenic.
_Symptoms._ There is chronic indigestion, emaciation, hide-bound,
depilation, red or weeping eyes, chronic diarrhœa, suppression of milk
in cows, muscular weakness, paraplegia, soreness of the gums,
salivation.
The _lesions_ are essentially the same only less intense than in the
acute form. Hugo found in the intestines of poisoned animals a slimy,
serous, grayish white fluid, and a false membrane like a frog spawn
streaking the intestine. Later this may be dense like a diphtheritic
membrane. There was fatty degeneration of the liver and of the gall
bladder epithelium. Injection of the capillary vessels of the brain and
pia, and effusion into the ventricles and on the surface of the brain
were found in dogs.
_Elimination._ Arsenic is eliminated mainly in the urine, but also in
part in the bile and perspiration.
_Tests for Arsenic._ When taken in the solid form it may be found
undissolved on the gastric mucosa.
If burned on red hot charcoal or iron it gives out the odor of garlic.
Marsh’s test consists in evolving arseniureted hydrogen from zinc and
sulphuric acid to which a little of the suspected liquid has been added.
A flask is taken having a cork conveying two tubes, one a funnel
reaching nearly the bottom of the flask, and the other a delivery tube
of some length and provided with a chloride of calcium bulb, and at its
end turned up at right angles and drawn out to form a narrow orifice.
Pieces of zinc are placed in the bottom of the flask, and sulphuric acid
is poured upon these through the funnel. This causes the evolution of
hydrogen. The suspected liquid is now added, and the gas issuing from
the delivery tube having been lighted, a piece of cold white porcelain
is held above and a short distance from the flame. A dark metallic spot
of arsenic is obtained. The stain obtained by antimony differs in being
formed more closely to the flame, in volatilizing less rapidly under
heat, and in forming a black or orange instead of the canary yellow
sulphide when subjected to a stream of H_{2}S. with gentle heat.
Chloride of lime dissolves the arsenic stain but has no effect on the
antimonial one.
_Treatment._ Avoid the causes. Employ the antidotes in small doses once
or twice daily. Check the diarrhœa by mucilaginous agents, and nourish
the animals well.