The regulative action whereby in health an excess of chlorides is quickly eliminated by the kidney is for some reason suspended during various diseases, and the condition of hyperchlorination is comparatively common.

Experiments on animals have demonstrated that an excess of chlorides introduced into the circulation is not able to escape with sufficient rapidity through the emunctories, but as the blood refuses to tolerate more than a certain proportion, the excess is excreted, so to speak, into the tissues, and therefore chlorine accumulates in the system. It has been sought to explain this phenomenon by stating that the chlorides combine partly with the albumins of the blood, which are increased during disease, and so form compounds incapable of excretion by the kidneys. But no increase of chlorides can be noted in the blood except for a few hours after absorption, although hyperchlorination is always associated with a heightened specific gravity of that fluid.

The retention of chlorides in the tissues has been explained in various ways, one or more of which may be in operation at the same time. It is not always dependent on inefficient renal activity, although the diseased kidney probably is less capable of excreting chlorides than the healthy kidney. Probably it is induced by interference with metabolic activity, for it is known that retention of chlorides may be secondary to the presence in excess of other producers of disassimilation. Besides, the retention may be local, as in ascites.

Widal has shown that a diseased kidney is relatively impermeable to chlorides and the products of nitrogenous metabolism, and cases of renal disease have been classified in accordance with difficulty of excretion of chlorides, of urea or of both substances. In the case of chloride of sodium, the salt passes back into the tissues to keep the tissue fluids isotonic with the blood serum. Urea, on the other hand, remains in the blood until its partial pressure or percentage proportion is sufficiently high to enable its ions to be absorbed by the renal cells and thus excreted, or in any case until the urea-pressure is high enough to force a passage. As chloride of sodium thus accumulates in the tissues and urea in the blood, it is easy to distinguish the two conditions, because in well-marked chloride retention there may be no excess of urea in the blood. If there be in the blood 2 to 4 grains of urea to the pint of serum (.3 to 600 grams), we are dealing only with chloride retention, but if we find 8 or more grains to the pint (.6 to 600 grams), then there is nitrogenous retention, while if it reaches 20 or 30 grains (1.6 or 2 to 600 grams), then death is imminent or probable.

Excess of chloride of sodium in the body raises the blood-pressure, although this may be only temporary. This saline hydration then induces oedema and may even cause albuminuria, but as it is stated to diminish the toxicity of certain endogenous poisons it may act as a defensive agency. A local excess is always irritating and may induce emesis or purgation. Physiological saline solutions are not painful because they are isotonic to the vital media, whereas hypertonic and hypotonic solutions generally create discomfort.

Moderate doses of salt, i.e., from 2 to 4 grams per day, increase metabolism and appetite, but they have also a tendency to diminish digestive activity. Although a sufficient quantity must be taken to keep up the supply of hydrochloric acid, still it is hardly possible to add too little to the food, and people have been known to exist for years without adding a grain to their vegetarian diet. Even when partaken of to excess, e.g., in diabetes, the body sustains no injury because it is easily excreted. In such conditions, however, it may irritate the digestive and other mucous membranes, and it is notable that diabetics and glycosurics are prone to attacks of nasal, pharyngeal, and bronchial catairh. Christison reported a case of death in a man twenty-four hours after having swallowed a pound of common salt.

A hyperchloric diet excites the appetite, stimulates diuresis where the patient is free from chloride retention, and fixes water in the tissues where there has been emaciation from dehydration. For this purpose, for example, in infantile enteritis Mery proposes the following clear soup: Carrots and potatoes 60 grams, turnips 25 grams, peas and beans 25 grams, water 1 litre. Boil these ingredients for four hours, drain off the water, and add salt in the proportion of 5 grams to the litre. When this is prepared fresh and given to children with choleraic diarrhoea (infantile enteritis), it fixes water in the tissues.

In his investigation on Bengali prisoners, who, it may be recalled, were pure vegetarians, Major McCay concluded that a large ingestion of salt in the diet is accompanied by an increase in the body-weight, an increase in the excretion of the urine, and a marked increase in the amount of salt eliminated by the skin. The quantity of chlorides in the faeces was constant, had no relation to the amount in the diet, and in any case was very small, only half a gram daily. He noted that there was practically complete absorption of the salt added to the food, whether the amount was large or small. He suggested that the salt ration should be regulated by the quantity excreted by the skin, and when this is found to exceed normal limits a reduction should take place in the allowance.

Engel's observations are of undoubted interest in this connection. He injected into the veins large quantities of 6 per cent. chloride of sodium solution, and found that all the tissues except the bones became more watery. The muscles, which represent about 40 per cent. of the weight of the body, absorbed quite two-thirds of this water and yet continued to perform their normal functions.