6. Death; pupils of the eye are seen to be dilated.
Aconitina has thus a powerful action on the brain, and on the nerves generally. The flow of saliva seems partly to arise from a paralysis of the fauces. The animal makes ineffectual attempts to swallow, and breathes spasmodically. By a small dose the anæsthesia would probably be produced, without the other effects. On examination of the body after death the lungs are found to be healthy, but shrunken and bloodless; the trachea contains much frothy mucus, which may possibly have flowed into it on account of the palsy of the glottis; the cavities of the heart are full; the mucous membrane of the stomach pale. It seems then that the immediate cause of death is paralytic syncope,—a loss of power in the heart. As the mucous coat of the stomach evinces no trace of congestion, it is probable that the vomiting is not caused by irritation, but by a sedative or deranging action on the function of the Vagus nerve. (Vide pp. 242, 245.)
DIGITALIS.
Class II. Div. III. Ord. II. Sedantia Specifica.
Class IV. Ord. VI. Diuretica.
This important medicine has already been prominently noticed as one of the agents that exert a special sedative and deranging power over the functions of the Vagus nerve. It will only be necessary now to sum up shortly the details of its action.
It does not depress nervous force generally. It has no action on the brain, except as connected with the Vagus nerve. Neither does it affect the spinal cord, or the nerves of sensation or motion. Its most obvious action in small doses is to depress the force of the heart. It sometimes quickens the pulse, but always weakens it, and reduces its rate in the end. It therefore supplies us with a ready means of weakening the heart, whenever we desire to do this. In cases of hypertrophy, where the heart is too strong,—or in aortic aneurism, or active hemorrhage, where a forcible beat would be dangerous,—Digitalis may be used for this purpose. But it is especially useful in dropsies; for by its action on the heart, it diminishes congestion of the venous system, and by thus removing the pressure from the veins, it favours the absorption of the fluids effused. It should, however, be avoided in cases where there is very serious cardiac obstruction, or where the heart is habitually weak, and there is a natural liability to syncope. For the tendency of the medicine is to cause death by producing syncope.
Certain precautions are necessary in its administration. The patient should be generally confined to the recumbent posture; for if, while under the influence of Digitalis, he should suddenly rise, and the heart, already weakened, have further to contend with the force of gravity in the propulsion of the blood upwards, it may actually stop. The dose also should be cautiously regulated, and, if it do not operate at once, it must not be increased, or too soon repeated; for this medicine is apt sometimes to accumulate in the blood, and though several doses may perhaps be given without effect, they are afterwards liable at any time to be suddenly discharged upon the nervous system, and may then produce by their united action a dangerous result.
A considerable dose of Digitalis, as of Tartar Emetic, deranges the control of the Vagus nerve over the function of the stomach, and may in this way produce nausea and vomiting. There is no reason for supposing that it irritates the coat of the stomach. (Vide p. 93.)
The active principle of Digitalis is secreted from the system in the urine, and probably acts as a true Eliminative Diuretic. But it tends more powerfully to promote diuresis in another indirect way. Any thing which diminishes the pressure on the vascular system, as Digitalis, by weakening the force of the heart, tends thereby to promote absorption, and to increase the secretion of urine.