LEAD. 
§§ 823, 824.] 
obscure, but it is considered to have an effect mainly on the nervous 
centres. The paralysed muscles respond to the direct current, but not 
to the induced, leading to the suspicion that the intramuscular termina¬ 
tions of the nerves are paralysed, but that the muscular substance itself 
is unattacked. On the other hand, the restriction of the action to groups 
of muscles supports the theory of central action. 
The lead colic is due to a true spasmodic constriction of the bowel, the 
exciting cause of which lies in the walls of the bowel itself ; the relief 
given by pressure is explained by the pressure causing an anaemia of the 
intestinal walls, and thus lessening their sensibility. The slowing of the 
pulse produced by small doses is explained as due to a stimulation of the 
inhibitory nerves ; and, lastly, many nervous phenomena, such as epi¬ 
lepsy, etc., are in part due to imperfect elimination of the urinary excreta, 
causing similar conditions to those observed in uraemia. 
§ 823. Elimination of Lead. —When a large dose of acetate or car¬ 
bonate is taken, part is transformed into more or less insoluble compounds 
—some organic, others inorganic ; so that a great portion is not absorbed 
into the body at all, but passes into the intestines, where, meeting with 
hydric sulphide, part is changed into sulphide, colouring the alvine evacua¬ 
tions black. Some of the lead which is absorbed is excreted by the 
kidneys, but the search often yields only traces. Thudichum 1 states 
that in fourteen cases of lead-poisoning, in two only was obtained a 
weighable quantity from a day’s urine ; in the remaining twelve lead was 
detected, but only by the brownish colour produced in an acid solution 
of the ash by hydric sulphide. 
The elimination of lead by the kidneys is favoured by certain medi¬ 
cines, such, for example, as potassic iodide. Annuschat found in dogs 
poisoned by lead from 3-8 to 4-1 mgrms. in 100 c.c. of urine ; but, after 
doses of potassic iodide, the content of lead rose to 6*9 and even bo 14 
mgrms. Lead appears to be eliminated by the skin, being taken up by the 
epithelial cells, and minute, insoluble particles coming away with these 
cells. If a person who has taken small doses of lead for a time be placed 
in a sulphur-water bath, or have his skin moistened with a 5 per cent, 
solution of sodium sulphide, the upper layer of the epidermis is coloured 
dark ; but the perspiration excited by pilocarpin or other agency contains 
no lead. 
§ 824. Fatal Dose.— (a) Sugar of Lead. —It may almost be said that 
it is impossible to destroy human life with any single dose likely to be 
taken or administered. In three cases an ounce (28-3 grms.) has been 
taken without fatal result. Although it must be allowed that repeated 
moderate doses, extending over some time, are more dangerous to health 
and life than a single large dose, yet there seems to be in some individuals 
a great tolerance of lead. Christison has given -18 grin, in divided 
1 Pathology of the Urine, p. 550. 
