Common salt is too well known to require description. I proceed, therefore, immediately to treat of its effects and remedial uses.

Effects on the System

Common salt is essential to health. The irresistible and almost universal craving for it, both by man and the higher animals, is strong evidence that it has some important purpose or purposes in the animal economy; and this is confirmed by its invariable presence in the blood. But, while thus essential to the higher orders of animal existence, it seems to be noxious to some of the lower, and is even poisonous to the leech. What are its special uses is not satisfactorily known. To supply muriatic acid to the digestive process, and soda to the blood, are conjecturally ascribed to it as characteristic offices; but the probability is, that there are other important purposes, connected with the formation and preservation of the blood, which it is intended to fulfil, independently of chemical decomposition. it is probable that it may prove serviceable by increasing the solubility of albuminous substances. The want of it impairs the general health; and, as there is some reason to believe, disposes to a condition of the blood, analogous to that which characterizes low fevers, and favouring the occurrence of gangrene, and of passive hemorrhages. Dr. Probart, of England, relates the case of a patient affected with gangrene of the lungs, who had abstained from the use of salt for five years. (Transact, of Prov. Med. and Surg. Assoc, xvii. 351.) A belief, too, has long prevailed, that the want of salt in the food disposes to the development and propagation of worms in the bowels. But few opportunities are offered us for judging of the effects of an entire absence of common salt; for, even though it were not used as a condiment, or even in the preparation of food, yet it is so widely diffused in nature, that it is scarcely possible to eat and drink without receiving a portion of it into the system.

It has been thought that an excessive use of it gives rise to serious disorders of health, and among others to scurvy; as this disease is apt to prevail among seamen, who are often for a long time confined to the use of salted meats; but experience has shown that it is not the salt meat, but the want of fresh vegetable food that causes the disease; for, with a sufficient supply of the latter, salted food may be eaten to any extent without causing scurvy. Dr. Grarrod ascertained that one of the effects of chloride of sodium on meat is to expel the salts of potassa, which he found less in proportion in salted than in fresh meat; and he has rendered it probable that the want of the potassa salts in scorbutic blood is one of the circumstances which favour the production of that disease.

At present, it is believed that an excess in the use of common salt disposes rather to an elevated state of the vital processes, to increased fulness of the system, and a plethoric state of the circulation, than to the opposite condition of health. The experiments of Bischoff would seem to prove that it augments considerably the discharge of urea by urine, whence it may be inferred to stimulate the nutritive or metamorphic process in the tissues; and the researches of C. Voit tend to the same result. (B. and F. Medico-chir. Rev., July, 1862, p. 234.) in slight excess, salt promotes the appetite and invigorates digestion, and appears to operate as a tonic. More largely taken, it irritates the stomach, and, in very large doses, acts as an emetic, and sometimes as a cathartic, causing at the same time excessive thirst. it is even capable of producing poisonous effects in enormous quantities. Dr. Christison mentions the case of a man who took a pound of salt, and died in consequence, with symptoms of gastro-enteric inflammation.* in commencing convalescence from acute diseases of some duration, in which the system has received but a scanty supply of salt, I have found nothing more grateful to patients generally than a little salt ham, or salt dried beef, broiled in thin slices, and eaten with bread and a cup of black tea. it is often the first thing that the appetite and the stomach will receive, in the way of food; and it has seemed to me to act favourably, by improving the appetite and invigorating digestion.

Therapeutic Application

Common salt is used remedially for two purposes prominently; to produce irritation locally, and to operate as an alterative tonic to the system at large; and the two purposes are often jointly fulfilled.

* M. Goubaux, of Alfort, injected, in numerous instances, into the stomachs of dogs, quantities of common salt in solution, varying in proportion to the weight of the animal, from 1 to 105, to 1 to 408; at the same time tying the oesophagus. in every instance death ensued, in a period varying from an hour and a quarter to about 27 hours; and appearances of violent inflammation were found in the gastroenteric mucous membrane. {Archives Gén., 5e sér., viii. pp. 1, 190, 444, a.d. 1856.) - Note to the second edition.

In scrofulous affections, which are characterized by a deficiency of vital force, salt operates beneficially in various ways; and, in the treatment of these cases, the inquiry should always be made, whether the patient uses sufficient salt in his food, and, if not, care should be taken to correct the deficiency. The sea air, loaded as it is with salt, is noted for its favourable influence, especially in connection with sea bathing, in most scrofulous affections; we might, indeed, say in all, with the exception of phthisis, in which, from its irritant effect on the lungs, it sometimes acts injuriously. Few remedies are more efficient in the scrofula of children, whether affecting the glands, the joints, or the spine, than sea air and sea bathing. When the latter is not attainable, it may be imitated by the use of the salt bath, which often does good in the complaint. The bath may be cold, warm, or hot, according to the special indications. When reaction takes place readily, the first may be employed; when there is great debility, the last; in intermediate states, the second. Another mode in which salt is used in scrofula is by topical application to the tumours and ulcers. A poultice made with strong brine proves useful sometimes in dispersing obstinate glandular swellings. it not unfrequently produces irritation of the skin, and even a pustular eruption; but these effects probably contribute to the result.