Physiological action on nervous system. Sources: near smelting
furnaces on vegetation; paints; paint scrapings in manure and on
soils; lead packing of pumps, engines, etc.; sheet lead; bullet spray;
wall paper lead; leaden water pipes or cisterns; lead acetate; painted
buckets; painted silo; lead compounds in arts. Experiments on animals.
Accidental poisoning: =horse=, fever, gray nasal discharge,
salivation, convulsions, paralysis, dyspnœa. =Cattle=, emaciation,
dyspnœa, palsy, tonic spasm of flexors of limbs, swollen carpus, death
in a few months. Young worst. =Sheep=, lambs paretic. =Swine= in pens
escaped, those at large suffered. Post mortem; lead or lead compounds
in stomach, or shown by analysis, in gastric contents, liver, spleen,
kidney, etc. Tests. Treatment: hydrosulphuric or sulphuric acid,
sulphate of magnesia or soda, antispasmodics; in chronic cases,
potassium iodide, bitters.
The physiological action of lead is exerted on the nervous system, so
that lead poisoning may be appropriately enough treated of as a disease
of the nervous system.
_Sources._ The sources of lead as a poison for animals are extremely
varied. In England in the vicinity of lead mines and smelting furnaces
it is deposited from the air in a fine powder, and consumed with the
vegetation. Herapath found that the deposit, in dangerous amount, began
half a mile from the chimney of the smelter and extended about half a
mile further.
A second source is in lead paints used about farms and the scrapings of
paint pots thrown out with manure and spread upon the fields. These lead
combinations will last for years in the soil or on the surface, being
plowed under one year and turned up again the next when the occasion of
their presence has been completely forgotten. In one case I found the
red lead paint marked by the tongues of cattle at the back of an
abandoned cottage the fence around which had been broken down. In
another the scrapings were found in an orchard which had been near and
convenient for throwing them out. In a third case a paint can hung on
the branch of an apple tree, well out of the way of the stock as the
owner fondly supposed, showed in its contents the marking of the barbed
tongues of the cattle. In a fourth case a barrel of paint was set under
the barn where there was not height enough to admit the matured cattle,
but it bore the marks of licking by the young stock, and they alone died
but in such numbers that the owner concluded it must be the
“Rinderpest.”
The lead packing from the joints of pumps, engines and other machinery,
thrown away around works and mines, is a common source of the trouble. I
once found large quantities in the gastric contents of cows that had
died around a coal mine in Ayrshire, Scotland.
Sheet lead—tea-chest lead—is another common source of the poison. This
is thrown out, scattered with the manure on the field, and will resist
the elements for years but dissolves when taken into the acid stomach of
the animal.
The spray from bullets in the vicinity of rifle butts is another common
cause of the poisoning.
In one instance I have seen a cow poisoned by eating some
lead-impregnated wall paper which had been carelessly left in the
stable.
Less frequently the poisoning comes from drinking water carried in
leaden pipes, or left to stand in a leaden cistern. The softest
waters—rain, snow, distilled water—are the most liable to this
impregnation. The hard waters containing carbonates, sulphates or
phosphates, tend to be decomposed, the acid uniting with the lead to
form comparatively insoluble carbonates, sulphates or phosphates of
lead, which protect the subjacent lead against solution. The hardness of
the water is not, however, a sufficient safeguard, as iron, solder, and
other agents present in the lead as an impurity or merely resting upon
it, are sufficient to set up a galvanic action resulting in solution.
The salts of lead may find direct access to the animal, as in the case
reported by Gamgee in which a farmer used a barrel which had contained
acetate of lead for mixing the feed given to his stock. A somewhat
similar source of poisoning is found in the use of buckets or silos
which have been painted inside, and scale off in contact with hot water,
etc.
Blythe enumerates the following compounds of lead as employed in the
arts:
1st. Hair dyes which have a basis of litharge, acetate or carbonate of
lead in combination with lime and other agents.
2nd. White lead in its various forms is carbonate of lead.
3rd. Newcastle white is white lead made with molasses vinegar.
4th. Nottingham white is white lead made with sour ale.
5th. Miniature Painter’s white is lead sulphate.
6th. Pattison white is an oxychloride of lead.
7th. Chrome Yellow is impure chromate of lead.
8th. Turner’s Yellow, Casella Yellow, Patent Yellow is oxychloride of
lead.
9th. Chrome Red is a bichromate of lead.
10th. Red Lead is the red oxide of lead.
11th. Orange Red is an oxide obtained by calcining the carbonate.
12th. Nitrate of Lead is much used in calico printing.
13th. Pyrolignite of Lead is an impure acetate used in dyeing.
14th. Sulphate of Lead is a by product in the preparation of acetate of
aluminium for dyeing.
_Forms._ Lead poisoning occurs in acute and chronic forms. The two
forms, however, merge into each other and are largely convulsive and
paralytic.
_Experimentally._ Harnack found that 2 to 3 mgrms. in frogs and 40
mgrms. in rabbits caused increased intestinal peristalsis, diarrhœa, and
paralysis of the heart. Dogs had choreic symptoms. Gusserno gave 1.2
grm. to rabbits and dogs respectively, and produced emaciation,
shivering and paralysis of the hind extremities. Rosenstein with 0.2 to
0.5 grm. obtained in dogs similar symptoms with epileptiform
convulsions, and Heubel had symptoms of colic in a few cases.
=Casual or Accidental Poisoning.= Metallic lead is slowly dissolved and
therefore large doses of this may be taken in without visible ill
effect. Shot has often been given to relieve the symptoms of broken wind
in horses, and a dog at the Lyons Veterinary School took four ounces
without visible ill effect. When finely divided, however, as in sheet
lead or the spray of bullets it presents a much more extended surface to
oxygen and acids, and in the acid stomach of monogastric animals, or
even in the organic acids of the rumen it is dissolved in quantity
sufficient to prove poisonous.
_Symptoms in Horses._ Shenton thus describes his cases. “There was a
rough, staring coat, a tucked up appearance of the abdomen, and a
slightly accelerated pulse; in fact, symptoms of febrile excitement
which usually, however, passed away in about a week. About this time
large quantities of gray colored matter were discharged from the
nostrils, and saliva from the mouth, but at no time was there any
enlargement of the submaxillary, lymphatic, or salivary glands. Nor was
there constipation of the bowels, which appears to be nearly always
present in cases of lead poisoning in man. Fits and partial paralysis
came on at intervals; and when the animals got down they often
struggled, for a long time ineffectually, to get up again. The breathing
up to this time was pretty tranquil, but now became so difficult and
labored that the patient appeared in danger of suffocation. The pulse
was in no case above 60 or 70, and I ascribe the difficulty of
respiration to a paralyzed state of the respiratory apparatus. The
animals did not live more than two or three days after these symptoms
appeared. The _post mortem_ appearance varied but little. The lungs and
trachea were inflamed; the lungs engorged with large quantities of black
blood; the trachea and bronchia filled with frothy spume. In all cases
but two the villous part of the stomach presented isolated patches of
increased vascular action, and in all cases the intestines, and
especially the large ones, were inflamed. The blind pouch of the cæcum
was nearly gangrenous. There was nothing remarkable about the liver,
spleen or kidneys, except that they were of a singularly blue
appearance.”
_Symptoms in Ruminants._ These are described by Herapath as following
the erection of lead smelting furnaces in the Mendip Hills in
Somersetshire. There were stunted growth, emaciation, shortness of
breathing, paralysis of the extremities, particularly the hinder ones,
the flexor muscles of the fore limbs affected so that the animals stood
on their toes, swelling of the knees and death in a few months. Even if
removed to a healthy locality the victims failed to thrive. The effects
were most pronounced in the young. Lambs were born paralytic; at three
weeks old they could not stand, and palsy of the glottis rendered it
dangerous to feed from a bottle. Twenty-one out of twenty-three died
early. The milk of cows and sheep was reduced in quantity and quality,
and contained traces of lead. The cheese had less fat in it. The dead
showed the mucous surfaces paler than natural and the lungs had large
areas with abruptly circumscribed margins of a dark red color,
surcharged with fluid. A blue line appeared on the gum close to the
teeth, and from this a globule of lead could be melted under the
blowpipe.
In the cases that have come under my observation paralysis of the hind
limbs, emaciation and low condition, have been most prominent in the
chronic forms, while these have been complicated by torpor of the
bowels, blindness, stupor, coma, and more or less frequent paroxysms of
delirious excitement or convulsions in the acute. In the chronic cases
the blue line on the gums is an important symptom.
Herapath noticed that near the smelting furnaces pigs escaped if kept in
the pen but suffered if allowed to go at large. This is explained by the
presence of lead in the forms of oxide, carbonate and sulphate on the
herbage, hay and hedge rows, and in short, on all vegetation.
In _post mortem_ examination the stomach should be carefully searched
for lead in the metallic form as sheet lead, bullet spray, etc., for the
different forms of paint of which lead forms an ingredient, for the
discarded white lead packing of pipes and machinery, and even for solid
masses of metallic lead. This is especially necessary in the case of
cattle in which the morbid habit of eating non-alimentary matters is so
common, and for which the sweet taste of some of the lead compounds
seems to offer an attraction. The lead being long retained in the first
three stomachs in contact with acetic and other organic acids is
especially liable to be dissolved and absorbed in dangerous amount.
In the chronic cases especially, the test by electric current may
furnish a valuable pointer. In lead poisoning the muscles respond much
less actively to the stimulus than in the normal condition.
In resorting to analysis the following table from Heubel of the amount
of lead in the different organs of a dog may offer a guide to the
selection of an organ for examination:
Liver .03 to .10 per cent.
Kidney .03 to .07 „ „
Brain .02 to .05 „ „
Bones .01 to .04 „ „
Muscles .004 to .008 „ „
Professor George Wilson found the lead very abundant in the spleen, and
used it for analysis. He dissolved it in aqua regia over a slow fire,
cooled, filtered, evaporated, cleared, and boiled with dilute nitric
acid. Then filtered and dried again, dissolved in dilute muriatic acid,
and finally applied the color tests. With hydrosulphuric acid it gives a
black precipitate, with sulphuric acid, a white, and with potassium
iodide or bichromate a bright yellow. Or from the solution of the
chloride the lead may be obtained as a metallic deposit on zinc from
which it can be fused into a minute globule on charcoal.
In the _treatment_ of lead poisoning the first object is to prevent the
further solution of lead in the alimentary canal and to carry it off. To
fill the first indication, hydrosulphuric acid or sulphuric acid may be
administered to form respectively the insoluble sulphide or sulphate. As
a purgative, sulphate of magnesia or soda should be preferred, as
favoring at once elimination and the formation of an insoluble
precipitate. Large doses are usually desirable, especially in ruminants,
because of the bulky contents of the stomach and the torpor of the
alimentary canal. If griping is a prominent symptom opium or other
antispasmodic must be added.
In chronic cases, after the evacuation of the contents of the alimentary
canal small daily doses of potassium iodide will serve to dissolve the
lead out of the tissues, while sulphates may be given in small doses to
assist in elimination from the bowels and to prevent reabsorption. The
treatment by potassium iodide is equally applicable, to assist in the
elimination of the lead that has passed into the circulation and
tissues. The doses, however, should in any case be small to avoid the
sudden solution of a large amount of lead which had been deposited in
the tissues in a comparatively insoluble form. The sudden entrance into
the circulation of any large amount of such lead would induce a prompt
return of the toxic symptoms. A continuous exhibition of small doses is
the course of wisdom and safety. The bowels should meanwhile be kept
somewhat relaxed by small doses of sodium or magnesium sulphate. As a
general tonic a course of bitters may be called for, especially when
torpor or emaciation is pronounced.