We have now to notice the effect of iodine on the nervous and muscular systems, and this is by far the most interesting part of our paper. It is that also on which the greatest degree of doubt and uncertainty rests.
The nervous and muscular systems are peculiarly exposed to the irregular action of this medicine. In certain persons, indeed, of peculiar habits of body, it cannot be exhibited so as to affect the constitution in any manner, without in some shape or other producing unpleasant nervous symptoms, such as dimness of vision, indistinct hearing, fallacious touch, insomnia, breathlessness, palpitation, and all the countless forms of inward nervous derangement. But the symptom to which we shall more peculiarly confine our attention, is a degree of tremor which generally comes on when the patient is under the full constitutional influence of iodine. This symptom may be reckoned a good gauge of the degree of nervous excitement which has taken place, and it is seldom or never absent when that excitement has proceeded to any considerable degree. It generally begins by a slight trembling of the hands, resembling that which takes place from the poison of lead; and if the medicine be incautiously continued, the larger muscles of the arms, legs, and back become affected. When in this state, the patient can with difficulty walk, and his progression is a tottering uncertain motion. He cannot carry any thing straight to his mouth, but the hand moves in a zig-zag manner, and with difficulty arrives at the mouth at last. This complaint is generally attended with a hurried circulation, and a small thready pulse. There is commonly great suffering at stomach and confined bowels.[2] When nervous affection first appears the medicine must be most diligently watched, and if the symptoms seem to increase, its use should be instantly put a stop to. If rashly persevered in, the symptoms I have described above will certainly be excited, and then it is vain to withdraw the medicine; the complaint goes on progressive for weeks and months, even though its exciting cause be abstracted; and when it does at last begin to diminish, the amendment is so slow and gradual that the patient is scarcely conscious of the relief he receives. I saw two cases of this kind with Dr. Peschier of Geneva, in which the patients had suffered more than twelve months, and yet their sufferings had undergone little mitigation. It is of some importance not to provoke a complaint with so much difficulty allayed; and no one who has not seen it can have an idea of the slow and imperceptible degrees by which it steals on the patient. Its first advances generally escape his observation as well as that of his physician. A slight trembling of the fingers, quivering of the eye-lids, occasional subsultus of the tendons of the fingers, arms, and legs, are generally the first symptoms observed, and it behoves us to be constantly on the watch for them. I have always obliged my patients to raise an empty glass or any light object to the head. By this means the smallest degree of unsteadiness in the hand will commonly be detected. I recommend a light object to be used for this purpose, because a heavy one tends to give steadiness to the muscles and to disguise the complaint.
This effect of iodine is frequently complicated with the choleric complaint I have already described; but it is evident that their proximate cause is different, since they also exist separately. The nervous affection is most common, if I may trust my observations, in the mobile constitutions of women; at least nine out of ten cases, which I have seen, were in women, and by far the greater number in young nubile girls. In the latter cases the disease generally excites some hysterical symptoms.
This affection differs from chorea. The patient has no difficulty in keeping the affected limbs steady, if not called upon to exert them, and in general exertion is irksome and painful. Like chorea, however, it is always attended with a constipated condition of bowels. The evacuations, also, are uniformly hard, scybulous, and dark coloured. There is certainly a considerable resemblance between the two diseases, but it would be too much to assert that what has been called their proximate cause, or their nature, is the same. Such an idea, however, has been adopted by more than one physician who has seen these cases along with myself. I mention this, not in order to give weight to the opinion, but in order to give my readers a more distinct notion of the form, which the affection we have been considering sometimes assumes. A statement of this kind is more graphical than many descriptions. Mr. Orfila, whose industry and ingenuity in the study of poisons are well known, has not neglected to examine and note the effects of iodine when given in a large dose. He gave it to different animals in the quantity of a dram and two drams. They were in general seized with violent and frequent vomiting. When the contents of the stomach were not soon thrown off, or were altogether retained, the poison was much more speedily fatal. The animals do not seem to have been affected with any other very remarkable symptom. It is stated that they were much dejected, and manifested suffering, though they did not howl, were not paralyzed or convulsed, and were not affected with any of the more violent symptoms by which poisons commonly show their action on the living body. It is plain that much light is not thus thrown on the effects of iodine when exhibited as a remedy; yet when considered along with the appearances after death, we still find a certain analogy. The stomach was generally found corroded by small ulcers of a linear form, which had eaten through the mucous coat. Those parts, also, which were most exposed to the action of the poison, were thinner and more transparent than the others, and were easily torn asunder. The mucous membrane in the neighbourhood of the pylorus was found much inflamed, swelled, and covered with a crust of coagulated lymph.
The affection of the alimentary canal which we have described above, is plainly to be ascribed to the acrid operation of iodine on its mucous membrane. I have never witnessed it in any considerable degree when this medicine had not been taken internally. But I have seen slight pains of stomach, accompanied with copious bilious evacuations, attend its external use. These never proceed to the degree of violence which marks the internal exhibition. Indeed, it is rare to see them in any considerable degree disturb the comfort of the patient. It is not thus when taken into the stomach. The case of the young lady related above, sufficiently shows its deleterious influence. I have never seen any disease of the bowels which more closely resembled the terrific descriptions given by the physicians of India, of the sufferings from the cholera of that country. Yet no medicine varies more in its effects than this. Some persons take it in large doses for a great length of time with perfect impunity; while others, from that peculiar, undescribed and unintelligible state of constitution, called by physicians an idiosyncrasy, are speedily and violently affected by very small doses. Mr. Magendie, whose accuracy is well known, states that he had swallowed a spoonful of the tincture, containing about a scruple of iodine, without any bad effect ensuing. A child, also, four years old, swallowed by mistake a tea-spoonful of the same preparation with equal impunity. These are extraordinary instances, for I have received the account of the death of a fine boy ten years old, who did not survive many hours after having swallowed the largest of the above doses. And a strong man who took this medicine, under my own care, in doses of half grains three times a-day for one week only, was very soon affected in such a manner, that, had the medicine not been immediately interrupted, the most lamentable consequences might have ensued. When this medicine is given internally, and it is often necessary that it should be thus exhibited, it must be used with extreme caution, under the sanction and observation of those who are able to watch its effects, and who are experienced in its virtues.
I have never seen a case in which the mismanagement of iodine proved fatal, and cannot, therefore, say whether its long continued use ulcerates the mucous membrane of the stomach in the human body, after the manner described by Orfila. I have no reason to believe that it does, unless the extreme violence of the symptoms, and the obstinacy of the vomiting, should by some be reckoned proofs of such a state. I certainly, however, am inclined to believe that the last mentioned symptom proceeds from inflammation and occlusion of the pylorus, which Orfila describes as the effect of poisoning by iodine.
It is a much more difficult task to discover a probable explanation of the manner in which iodine disturbs the actions of the nervous system. The rationale of diseases, even when we are best acquainted with their history, is obscure and unsatisfactory. Here it is better at once to stop short, and confess our ignorance, than, by adventurous speculation and daring theory, lay a foundation for mistakes in practice. This subject certainly presents a fine field for hypothesis, and a tempting one to a theorist. But we leave our readers in possession of the facts, and trust they will not use them with less caution than ourselves. One thing only seems probable, that is by its operation on the brain, either immediately, or through the agency of the nerves, that the effects we are considering are produced. The similarity of this effect of iodine to the mercurial erethismus, so well described by Mr. Pearson, will be evident to all, and is an analogy deserving of attention and study. I have seen many instances of gilders in Paris and Geneva affected with mercurial erethismus, closely resembling the erethismus from the use of iodine.
Our most important consideration is the cure of these painful affections. In the choleric disease the first remedy of all, and that without which we can have little hope of subduing the disease, is opium. If called early to the patient, before the bowels have yet thrown off their acrid contents, I have generally waited a little before exhibiting opium. I have done this for two reasons: First, that I might be certain of all acrid matters having been removed from the alimentary canal before the prescription of a medicine to quiet its irritation; and, secondly, because it is with great difficulty that the opium is retained while the extreme irritation of the disease is going forward. Emollient and diluting injections will in these cases be found most useful auxiliaries, both by washing out the inferior portion of the gut, and by quieting the violent action of the stomach. Hemlock and hyoscyamus sometimes succeed when opium fails. The case related at page 7 was much relieved, indeed I may say that the young lady’s life was saved, by a quarter of a grain of acetate of morphium given every half-hour. Every other form of opium was tried without effect; they were not even retained an instant on the stomach. The acetate of morphium alone could be taken, and it effectually restrained the disease, which must otherwise have very soon terminated the life of the patient. This medicine has not, however, answered my expectation in other cases. I have tried various bitter and astringent medicines in union with opium, but have found them uniformly injurious during the first stage of excitement and exacerbation. Afterwards, when the disease has in some degree abated, this class of medicine will be found useful. I cannot too strongly caution my readers against the use of purgatives in such cases. However gentle they may be, their effect is uniformly and most decidedly noxious. In the first and acute period of this affection of the alimentary canal, it is almost impossible to quiet the disturbance which a purgative occasions. A remedy which ought never to be neglected is the warm bath. It will be found a most powerful coadjutor in restraining the violence of the spasms, and in moderating the perturbed action of the stomach.