It is an unquestionable fact that purins are poisons to many people, as they most certainly are to Dr. Haig. They are mainly excreted by the kidneys as uric acid, and this is the keystone of the superstructure he rears on the fact of his intolerance for purins. As a student he was a martyr to headache, and found that by diminishing the quantity of flesh foods he produced an amelioration of this troublesome ailment. He noted that the headaches were always accompanied by a large excretion of uric acid in the urine, and that when he was able to reduce the amount of this excretion he could assuage the headache. This he effected at first by administering a dose of mineral acid, and coincident with the relief, he often detected pricking and shooting pains in his joints and elsewhere. At the same time he discovered that the administration of an alkali increased the uric acid in the urine and induced the return of the headache. He thus argued that uric acid was directly or indirectly the cause of the headache and other allied conditions, as well as the most important factor in rheumatism and gout. Thus at the very outset, on what must be confessed as rather insufficient data, he enunciated the doctrine that there were two great classes of uric-acid diseases - those which, like headache, were due to its excess in the blood and therefore in the urine, and those, like rheumatism, due to its excess in the joints and fibrous tissues and its diminution in the blood and urine.

He likewise noted that the headache was associated with high blood-pressure, and this suggested that uric acid might in some way exercise some controlling influence over the circulation. Reflecting on the well-known facts of Raynaud's disease, and watching the fluctuations in his own capillary circulation, he concluded that uric acid controlled the capillary circulation of the body, and that the greater the quantity of uric acid there is in the blood, the more sluggish is the capillary circulation, whereas the less uric acid there is in the blood, the freer and more responsive is the capillary circulation. The uric acid excreted in the urine, he considered, was an index both to the amount of uric acid in the blood and to the rate of the capillary circulation. He therefore inferred that the blood in Bright's disease, in cerebral haemorrhage, and whilst it was under the influence of alkalis and salicylates, would always contain an excess of uric acid, whereas in fever, or after the administration of acids, it would always display a scanty content of uric acid. He professes to demonstrate this by mixing a little of the blood with chloride of ammonium solution, when the uric acid is precipitated in the form of granules, and this, taken in relation to the number of erythrocytes, gives, he asserts, an absolutely correct index of the amount of uric acid in the blood. This, however, he considers is a work of supererogation, as the same fact could be substantiated by what he calls the capillary reflux - i.e., the time in half-seconds taken for the return of the blood to the capillaries from which it had been ejected by the pressure of the finger. It is quite fair to observe, at this point, that although Garrod has established the fact that the blood of gouty persons contains uric acid, no one, apart from the above testimony, has been able to find it in normal blood. The ammonium chloride reaction and the capillary reflux must, therefore, be open to an interpretation other than that suggested by Dr. Haig, as these phenomena can apparently be elicited in the blood and circulation of normal people.

Recognising that uric acid was a normal product of tissue katabolism, he postulated that the particular quantity due to this cause could always be excreted without harm to the organism, but the inclusion of any further quantity in the food was at least liable to be accompanied by its excessive presence in the blood or tissues. He even goes further now, and asserts positively that this additional food purin always damages the body in some way, and in particular in a colloidal form blocks the capillaries, obstructs the flow of blood in the veins, and so, when the heart is strong, induces a rise of blood-pressure. In people whose blood is fairly free from uric acid such a small quantity as 3 grains of uric acid introduced into the blood will produce to a slight extent this condition, which he calls collaemia, whereas when a large dose, say 30 grains, is swallowed, quite a different result is brought about. This quantity is too great to be dissolved by the blood, and so, carried to the liver, it is retained there, the blood and urine are cleared, the capillary reflux quickened, the metabolism is stimulated, and a feeling of strength and power results, as if a tonic had been taken. These statements hardly coincide with the well-known fact that the administration of uric acid by the mouth is quickly followed by its excretion, chiefly as urea, although a distinct proportion of it is eliminated unchanged in the urine.

This, in his opinion, is the explanation of the stimulating effects of meat soups, beef-teas, gravies, and acids, which drive the uric acid out of the blood into the liver and other organs. This stimulating effect is only temporary, and is quickly followed by depression, with a slow capillary reflux, due to the uric acid stored up in the liver and tissues being dissolved out. The blood becomes flooded with uric acid in a colloid state, and there is an excessive excretion of the uric acid in the urine. By eschewing foods containing purins, it is possible to increase the solvent power of the blood for uric acid, and, as it is quickly excreted, it is never stored up in the liver or other tissues. The result is a fall in the blood-pressure, a quicker capillary reflux, and what he calls an increased blood decimal.

He states that uric acid is always found in the body in a definite quantity in relation to urea, about 1 to 35, so that an excretion of 420 grains of urea should be accompanied by 12 grains of uric acid. If an individual with such quantities were to increase his ingestion of purins, then his blood would not be capable of dissolving all the uric acid formed, and as it could not be excreted, it would be stored up in the tissues. The blood can dissolve uric acid in proportion to its alkalinity; but being always alkaline it can always dissolve a certain quantity. Its solvent power for uric acid can be increased by taking substances which increase its alkalinity, and diminished by substances which reduce its alkalinity, or which form directly an insoluble compound with uric acid. There is, he declares, a continual interchange of uric acid between the blood and the tissues. In the morning, the blood is a good solvent of uric acid, and takes it up from stores deposited in the body; in the evening it is a bad solvent, and gives it up to the tissues. Hence headache and irritability are common in the morning, while high spirits prevail in the evening. So also arthritis is worst then and in the cold season of the year. Uric acid in the tissues produces irritation; but for this purpose it must be in solution, as solid deposits of biurate of soda cause no discomfort.

Uric acid, or its equivalent, is contained in fish, flesh, fowl, and eggs which are not quite fresh, to the extent of 6 grains to the pound. Xanthins in peas, beans, lentils, peanuts, asparagus, and mushrooms, may reach 16 grains per pound, and as much as 175 grains are contained in a pound of tea, half this quantity in coffee, and one-third of the amount in cocoa.

He affirms that as uric acid controls the circulation, it likewise exerts its sway over the metabolism. Oxygen not being able to reach the tissues from the blood during collaemia, the albumin of the tissues is not properly burned up into urea, acids, etc, and so is excreted unchanged by the kidneys. Subjects of the collaemic group of diseases may be recognised by the puffy condition of the skin and lower eyelids, in some cases amounting to oedema. The eyes are likewise unduly prominent, a sign of high blood-pressure, notably so in exophthalmic goitre. In such cases the blood-pressure may be as high as 180 mm. Hg, and so long as the heart is strong there is no danger of the rupture of blood-vessels. All sorts of diseases are therefore likely to arise - dyspepsia, liver disease and diabetes, albuminuria, depression, fatigue, neurasthenia, etc, and Dr. Haig goes the length of saying that by examining the capillary reflux without seeing the face at all he could indicate what the physical, mental, and moral nature are likely to be. The precipitation group of diseases includes gout, rheumatism, and all local inflammations of fibrous tissues, such as bronchitis, colitis, neuritis, appendicitis, etc.

It is quite impossible to do justice to the theory in this fragmentary account of it, and despite the blemishes of the treatise, I would counsel every medical man to study it carefully. It is a perfect mine of valuable clinical facts, and is of special interest to the man who has forgotten much of his pathology, because it provides him with a form of clinical pathology which is particularly useful in therapeutics.

Criticisms Of The Theory

The obvious remedy for the conditions which have been described seems to be to exclude all purins and xanthins from the diet. When disease has arisen from a prolonged course of the ingestion of the poison, all that is necessary is to refer it to one of the two groups and administer solvents or precipitants of uric acid respectively. The whole thing appears to be simplicity itself, and one is apt to become enthusiastic to a degree in the application of the rule. Even when, after much patient research, you prove without a shadow of a doubt that the bulk of the purins and xanthins ingested are as a rule easily excreted within forty-eight hours, you do not lose faith, and you look round upon the countless examples of healthy men and women who have lived to a good old age, and have triumphed over all the dangers of the foods which Haig places upon his expurgatorial list, as having become in some unaccountable way possessed of the true elixir vitae. After a few years' careful observation, however, you are not quite so sanguine as to the infallibility of the cure-all, and when you begin to investigate the matter carefully you find that the objections to the theory may be grouped under three different heads.