The first branch of this process is nearly the same with the one adopted in the last edition of the present work. The second is derived from a process lately proposed by Orfila.[[1089]]
The principles on which it is founded are these. 1. Of the numerous organic compounds formed by vegetable and animal principles with the salts of copper, all either dissolve in very weak acetic acid, or part with their oxide of copper to it. This was pointed out by me in my last edition. 2, Weak acetic acid, as already mentioned (p. [356]), has been shown by M. Devergie to be incapable of dissolving that copper which is contained naturally in the tissues, at least so as to render it discoverable by the subsequent steps of the process. 3, According to Orfila, copper naturally present in organic substances, is never indicated by the second branch of the process, provided the charred product of the action of nitric acid and chlorate of potash be not heated to incineration. It does not appear why the charring process, when so conducted, should separate adventitious copper, and not that which is present naturally. But the empirical fact may be accepted in the mean time, as it rests on apparently careful experiments.
Orfila does not use acetic acid in the first branch of his process, but merely infuses the suspected matter in cold water, and if copper be not thus found, he has recourse to boiling water. But this method introduces needless complexity; and besides neither maceration, nor boiling with mere water, will dissolve out the whole oxide of copper. Acidulation with acetic acid dissolves it all; and Devergie has shown that this advantage is gained without any additional fallacy arising from the possible presence of copper as a natural ingredient of the substance under examination (p. [356]).
Section II.—Of the Action of Copper, and the Symptoms it excites in Man.
The symptoms caused by copper have at least two varieties in their character. One class arises from its local action on the alimentary canal; the other from its operation on distant organs.
This double influence is proved by the experiments of Drouard on animals, published in his inaugural dissertation at Paris in 1802; and by those of Orfila in his Toxicology.
When Drouard gave twelve grains of verdigris to a strong dog fasting, he observed that it caused aversion to food, efforts to vomit, diarrhœa, listlessness, and death in twenty-two hours; and that the stomach was but little inflamed. When two grains dissolved in water were injected into the jugular vein of another dog, it caused vomiting and discharge of fæces in seven minutes, then rattling in the throat, and death in half an hour; and there was no particular morbid appearance in the body.—Half a grain killed another in four days; and in addition to the preceding symptoms, there was palsy of the hind legs for a day before death. Six grains of the sulphate introduced into the stomach killed a dog in half an hour, without producing any appearance of inflammation.[[1090]]
These experiments prove that it is not by causing local irritation that this poison proves fatal. But its mode of action is more distinctly shown in the later and more accurate experiments of Orfila. He found that twelve or fifteen grains of the neutral acetate generally killed dogs within an hour; and that besides the usual symptoms of irritation in the stomach, they often had insensibility, almost always convulsions, and immediately before death rigidity, or even absolute tetanus. He likewise remarked violent convulsions and insensibility when a grain of this salt was injected into the veins; and death was then seldom delayed beyond ten minutes. In no case was there any particular morbid appearance, except loss of contractility in the voluntary muscles.[[1091]] More recently results nearly the same have been obtained by Mitscherlich; and when doses of two drachms of sulphate of copper were given, he observed after death pale blueness of the villous coat of the stomach, mingled with brownness,—the apparent effect of chemical action.[[1092]]
Allied to these results are those obtained by my late colleague, Dr. Duncan, and by Mitscherlich, when the sulphate was applied to a wound. Dr. Duncan observed that death took place in twenty-two hours, and the body was every where in a healthy state. Mitscherlich found that a drachm of either sulphate or acetate proved fatal in four hours, with symptoms of extreme prostration. The experiments of M. Smith, repeated by Orfila, are at variance with these; for one or two drachms of the acetate applied to a wound in the thigh of a dog caused only local inflammation, and no constitutional symptoms.[[1093]]
It follows from the researches now detailed, that the salts of copper act in whatever way they are introduced into the system, and the more energetically, the more directly they enter the blood. The inquiries of Mr. Blake farther show, that when injected into the blood-vessels, they act with peculiar force in exhausting muscular irritability, and occasion death by paralysing the heart if they are injected into a vein. Six grains of the sulphate injected into the jugular vein of a dog reduced the force of the heart’s contractions, and fifteen grains arrested them in twelve seconds, leaving in the dead body distension of the heart, loss of contractility, and florid blood in the left cavities. Ten grains injected into the aorta through the axillary artery caused no sign of obstruction in the capillary system; and small doses of three or four grains occasioned vomiting, dyspnœa, and stiffness of the limbs; and immediately after death the muscles had lost their irritability.[[1094]]