604 
SECOND REPORT- 1862. 
tached, and consequently are all naked and exposed to the ac¬ 
tion of the water; when unemployed, however, and folded close 
upon the abdomen, the inner plate in each pair is almost co¬ 
vered by the outer one. 
Abstract of an Esssay on the Poisonous Properties of the Salts 
- of Lead. By Anthony Todd Thomson, M.D., Professor 
of Materia Medica, §c. in the University of London. 
The object of this Essay is to show the probability, that 
among the salts of lead the carbonate is the only direct poison ; 
and that the seemingly poisonous properties of the other salts 
of that metal depend on their conversion into this. 
The author commences his inquiry by the detail of a few 
historical facts, to show that the poisonous effects of the car¬ 
bonate of lead were known at an early period, and that the 
opinions respecting the poisonous properties of the other salts 
of this metal are of modern date. Paracelsus, who introduced 
the medicinal employment of acetate of lead, administered it in 
large doses with impunity; and instances are recorded in which 
persons have swallowed from one drachm to six drachms of the 
salt, without experiencing any injurious consequences. 
He then states some experiments which he made to deter¬ 
mine the affinity of the different salts of lead for carbonic acid; 
from which it appears, that subacetate and citrate of lead in so¬ 
lution have so powerful an affinity for carbonic acid, as to take 
it from the air, and all other substances containing it; that the 
affinity of the acetate for this acid is comparatively weak; and 
that carbonic acid effects no change whatever on the nitrate, 
muriate, sulphate, phosphate, and tartrate of lead. 
The next object of the author was to examine the effect 
which the three salts, convertible into the carbonate, produce 
upon animals. Eight experiments upon dogs are detailed, 
which led to the conclusion that these quadrupeds are bad 
subjects of experiments with the salts of lead. None of the 
dogs died. He endeavours to account for the deaths recorded 
by Orfila in similar experiments on dogs, b}^ suggesting that, 
as the doses were extravagantly large, the irritation excited in 
the stomach produced inflammation and death, in the same 
manner as common salt or any other salt in excessive doses, 
independent of any poisonous property. He also thinks that 
some fallacy may arise from placing a ligature upon the oeso¬ 
phagus, as under such circumstances the animal cannot be con¬ 
sidered to be in a natural condition. Eight experiments upon 
rabbits are next detailed. In the first experiment, six grains 
