- riments agree in showing that these poisons have a direct irritating
action, and a remote operation of an unknown kind; but the results obtained by different experimentalists differ as to some of the details. The acetate may be taken as a type of the whole genus.
Orfila found that it was hardly possible to bring dogs under the action of the acetate if swallowed in solution, because they speedily discharged it all by vomiting. But if the salt was given in powder in the dose of half an ounce, or if the solution was retained in the stomach by a ligature on the gullet, the symptoms produced were those of violent irritation in the first instance, succeeded by extreme weakness and death, sometimes in nine hours, more generally not till the second day or later. The appearances in the body were unnatural whiteness of the villous coat when death was rapid, and vascular redness when death was slower. The whiteness in the former case Orfila ascribes to chemical action. But as neither this appearance nor the redness in the latter case was considerable, while at the same time the symptoms were not those of continuous irritation, he was led to doubt whether the poison causes death in consequence of its irritant properties. And the phenomena observed by him when acetate of lead was injected into the jugular vein prove that death is owing to certain remote effects. Introduced through this channel thirteen grains killed a dog almost immediately, death being preceded by no other symptom except convulsive respiration; five grains killed another in five days, and the leading symptoms were weariness, languor, staggering, and slight convulsions, none of which symptoms appeared till the third day; and it is remarkable that in neither animal could he find any morbid appearance on dissection.[1] Mr. Blake states that large doses, such as a drachm, suddenly arrest the heart's action; but that small doses of three grains, injected into the jugular vein, cause diminished action of that organ, and afterwards gorging and hepatization of the lungs; and that when injected backwards into the aorta from the axillary artery, this salt occasions obstruction of the capillary circulation, indicated by increased arterial pressure,—and then an action on the nervous system, producing insensibility, violent movements of the tail, and at last arrestment of the respiration. It may be inferred from Mr. Blake's researches that lead obstructs both the systemic and pulmonary capillaries, that it acts powerfully on the nervous centre, and that it likewise depresses the heart's action when the dose is large.[2]
The experiments of Gaspard coincide with those of Orfila in assigning considerable activity to the acetate of lead when it is directly introduced into the blood,—the quantity of two or four grains generally causing death in three or five days.[3] The experiments of Campbell farther show that death may be induced by applying it to a wound, and that the symptoms antecedent to death resemble those remarked by Orfila when it is injected into a vein.[4] But the two
