That arterial hypertonus may be the result of dietetic errors there can be no doubt. The latter may operate in one of two ways : by causing the blood to be poisoned by the products of disordered digestion, and (when too much food is taken) by burdening the tissues with an excess of nutrient material.

When, as the result of defective digestion in the stomach or bowel, the blood is contaminated by the absorption of poisons from the digestive tract, the condition may be spoken of as indigestion toxaemia, and seeing that the chemistry of indigestion differs for each of its multitudinous varieties, it is obvious that there must be many different varieties of this kind of toxaemia. Of the numerous poisons with which the blood may in this way be contaminated some exercise a hypotonic, others a hypertonic, or constrictory, effect upon the arteries.

There can be no doubt that these vaso-constrictor poisons play a prominent part in the production of arterio-sclerosis. Russell, indeed, contends that they are responsible for most cases occurring independently of chronic renal disease, an association which gives to indigestion, "especially when associated with constipation, a significance which has not commonly been appreciated." The poisons most pernicious in this respect are, according to this authority, those resulting from the putrefaction of animal protein, a process which in his opinion is greatly favoured by constipation. Hence, in order to guard against that hypertonus which is the central feature in a large number of cases of arterio-sclerosis, the paramount importance of avoiding an excess of animal food and of securing a free daily evacuation of the bowels must be realized. Vegetable protein and carbohydrates he deems far less capable of inducing hypertonus than animal protein.

The personal factor has, of course, to be taken into account in this connexion, for, as Russell rightly insists, "If the big feeder and moderate drinker has a good digestion and free bowel evacuation daily, he may not develop arterio-sclerosis until late in life, while if the spare feeder and teetotaller is a dyspeptic or the victim of chronic constipation, he will suffer from premature arterial degeneration".

While emphasizing the prominent part played by indigestion toxaemia in the production of arterial hypertonus and the associated sclerosis, we venture to think that Dr. Russell attributes to it a too exclusive influence in this direction, and that, apart from renal disease, there are many species of morbid plasma capable of inducing protracted hypertonus besides those associated with diet and indigestion. Nor do we share his extreme views as to the role of animal as against vegetable food in the production of this condition. On the one hand we meet with persons who, although eating freely of animal food and habitually suffering from indigestion and constipation, yet exhibit quite low blood pressure readings; and, on the other hand, we encounter, independently of renal disease, instances of protracted hypertonus among persons who consume little animal food, who do not suffer from constipation, and who, to all appearances, seem to digest their food quite well - nay, whose blood pressure continues high during complete starvation.

In considering the effect of diet on vascular tonus we must assuredly take account of the vegetable as well as of the animal food. There is no reason to suppose that the behaviour of vegetable protein in the body differs essentially from that of animal protein. Nor can we exonerate the carbo-hydrates from all share in the production of hypertonus. They are, as is well known, a fruitful source of indigestion, and may, in this way, cause toxaemia, and so hypertonus; possibly also by giving rise to that condition of the blood which Dr. Francis Hare has termed hyper-pyraemia. In any case gouty conditions can often be benefited by curtailing the supply of starch and sugar, and although, as Sir Clifford Allbutt and others have rightly insisted, there is not necessarily a rise of blood pressure in gout, yet there often is, and as a matter of fact it is almost as important to pay attention to the carbo-hydrates as to the animal food in the treatment of high blood pressure due to dietetic causes. In treating hypertonus we may sometimes get better results from a highly animalized diet into which starch and sugar enter but sparingly than from a purely vegetarian diet, always providing that the total quantity of food is moderate. Moderation in diet is, indeed, a prime essential in the treatment of high blood pressure, not only because it favours efficient digestion and thus tends to minimize the danger of indigestion toxaemia, but because the tissues are less likely to be clogged with waste products on a moderate diet than on one which is excessive.

In obstinate forms of hypertonus it may be advisable to put the patient on a milk diet. This treatment, especially if conjoined with rest in bed, bleeding, and free purgation with mercurials and salines, constitutes the most efficient means of reducing a dangerously high tension. Milk diet is, however, apt to pall after a time; so also is a milk and farinaceous, or milk, farinaceous, and fish diet; and we may find that we get better results from an ordinary diet, if it is relished, than from any of these, always providing that it is moderate in quantity. It is possible that fish is less conducive to hypertonus than bird or butcher's meat. Some maintain that boiled meat is less objectional in this respect than roast, containing as it does a smaller quantity of extractives. For a similar reason soups are by some supposed to be contra-indicated in subjects of high blood pressure.

As regards liquors, alcoholic drinks should be either entirely avoided or taken very sparingly. It has been definitely proved that their immoderate use is a potent cause of arterio-sclerosis, as well as of fatty degeneration of the heart. It may not be unfitting to mention here that tobacco smoking tends to cause arterial hypertonus.

Water is the best drink for the subjects of high blood pressure. It should be moderately soft or distilled, and non-aerated. Weak China tea, unsweetened, may also be allowed. In some cases it may be necessary, especially in women, to increase the daily allowance of fluid; in others it may be advisable to reduce the quantity. The patient should not drink much with his meals but should take most of his drink on an empty stomach, about an hour before meal time, so as to allow the fluid to be absorbed into the blood before a fresh supply of food enters the stomach. This plan not only conduces to good digestion by preventing an undue dilution of the gastric juices, but allows any excess of fluid that may be absorbed to be eliminated from the body before a fresh meal passes into the blood.

How far calcification of the arteries can be averted by dietetic measures is, as Sir Clifford Allbutt has said, a contestable point: " In the first place calcification of the media is not ' arteriosclerosis ' in the usual sense of this name . . .; secondly, I do not know that if the media has entered upon the stage of necrosis leading to calcification this change is any further detriment. Indeed, Ludwig Weil's experiments indicate that thereby the vessel is even fortified. In any case, to try to prevent it by niggling at the lime in the food is like taking away a man's cash and leaving him his cheque-book".

Inasmuch as in certain affections of the kidney, notably Bright's disease, there is an undue retention of chlorides in the system, the question suggests itself whether it may not be possible to reduce a supernormal blood pressure by means of a saltless diet. All that we can say at present is that this plan of treatment appears worthy of trial.

Summary

By arterio-sclerosis is meant either atheroma or a diffuse thickening of the arterial wall. Setting aside primary calcareous infiltration of the media, which is essentially a senile change, most cases of diffuse arterial sclerosis centre round arterial hypertonus. This latter, when protracted, indicates a morbid condition of the plasma and one which, if long continued, will certainly lead to arterio-sclerosis. Hence the importance of recognizing hypertonus early. Just so far as we succeed in relieving the hypertonus, and so far only, shall we be successful in preventing or checking the occurrence of arteriosclerosis.

There are probably many morbid conditions of the plasma capable of causing hypertonus. One of the most familiar is that which occurs in association with granular kidney. Overeating and indigestion may also operate powerfully in the same direction, and hence, by careful attention to diet much may be done to guard against arterio-sclerosis.

Accordingly, when this condition is present we prescribe a diet which is easily digestible and no more than sufficient to meet the demands of nutrition, our object being to secure sound digestion and to avoid burdening the tissues with an excess of nutriment. Hence our advice to the subject of hypertonus practically amounts to this: "Eat in strict moderation whatever plain food you are capable of digesting easily." If this advice is stringently followed the patient is not likely to harm himself with animal food. We should, however, always inquire into the exact amount of animal food taken, and be careful to keep its supply within due limits. On the other hand, we may-find it needful to curtail the quantity of starch and sugar.

There can be no doubt that by suitably dieting subjects of high blood pressure much may often be done to reduce the pressure to within normal limits, and that, provided treatment is begun sufficiently early, we may in this way prevent the occurrence of arterio-sclerosis. Sir Clifford Allbutt, Dr. William Russell, and Dr. George Oliver are emphatic on this head.