At the present time, in existing text-books and otherwise, the subject of diet in its scientific and clinical aspects is studied from two standpoints and two standpoints only. These are: (1) from the point of view of the chemical composition of the food - that is to say, the amount of protein, fats, and carbohydrates and salts in the dietary; and (2) from the point of view of the caloric or heat value of the food.

In the course of the past few years the observations of the writer have shown the necessity of regarding the subject from a new standpoint, viz. -

(3) The influence of particular foods on the structure and functions of the tissues.

This subject is a very large one, and our knowledge of it is yet in its infancy; and what I propose this evening is to ask your attention to certain points in the effects of a rich protein or rich purin diet in relation to one disease (gout) and one organ (the thyroid gland).

My earlier investigations dealt with the influence of an exclusive meat diet, administered, uncooked, on the structure of the tissues, and notably the thyroid gland, kidneys, and mucous membranes.

These showed that the structure and functions of these tissues were as a rule modified, and some of these modifications were acquired by the offspring, and were associated in them with an increased susceptibility to disease, notably catarrh of the different mucous membranes. The results therefore showed (what, after all, might well be expected) that diet modified the "soil" in animals, and suggested that similar modifications in structure and function would hold good for man.

My results, and the conclusions drawn from them, have received a fair share of adverse criticism, firstly, from the experimental standpoint, and secondly, from the clinical.

Let us deal in the first place with the criticism of my fellow-clinicians. It was urged by clinicians in this and other societies, that it was not permissible to draw any deductions from the results of my experimental investigations applicable to conditions obtaining in the human subject It was urged that the facts of my dealing with (1) an exclusive meat diet, and (2) administering that diet in an uncooked form, were conditions so dissimilar to those in the human subject as to preclude any deductions being drawn from my results applicable to man. There is undoubtedly something in this criticism, but I think much less than is at first sight suggested. The matter, however, was essentially one for further investigation, from the experimental standpoint, along lines which would remove these objections, and this has been carried out, with the results to be immediately referred to.

1Chalmen Watson, Transactions of the Edinburgh Medico-Chirurgical Society, 1910.

A more serious criticism has been directed from the experimental standpoint. Thus Forsyth writes: -

"Accepting for the moment the conclusions of Chalmers Watson, it would be expected that the thyroid glands of birds of prey would show to a marked degree the features he has ascribed to excessive protein feeding. It should be found that (1) the thyroids of these birds consist of large vesicles filled with colloid, so that the intervesicular glandular tissue is diminished; and (2) that the thyroids of non-raptorial birds, when contrasted with them, show vesicles of comparatively small size, a not over abundant secretion of colloid, and an average amount of intervesicular glandular tissue. In the specimens I have examined I find that this relation does not exist, and that not only were the structural characters which we were assuming to be associated with meat feeding not specially marked in carnivorous birds, but in some cases the exact contrary was prominent." He then proceeds to demolish to his own satisfaction my position by concluding from these data that there are no peculiarities of microscopic structure referable to difference in their natural foods.

Forsyth, I think, fell into error in two directions. In the first place, he has drawn in the above statement a deduction from the facts and statements made by me which is entirely unwarranted. Further, he failed to recognise in dealing with birds dying in captivity in the Zoological Gardens, that many of the animals in virtue of their malnutrition and emaciation at death had been living on their own protein tissue. In such cases it does not matter whether the natural diet of the bird in question be exclusively vegetarian: the practical point is that at the time of its death it had been living on its own protein tissue. In the same way, I have no doubt that the thyroid gland of certain men and women whom we occasionally see in a miserable state of health and malnutrition from living on an exclusively vegetarian dietary of a very unfavourable kind will present a character similar to those associated in others with the ingestion of excess of animal protein food.

Forsyth's paper was published in 1907. Since that time I have carried out a further series of investigations into the effects of a rich protein diet on the structure of the thyroid gland and other tissues. The diet employed was a mixed one, consisting of minced ox-flesh, lentils, and bread and milk, the two former ingredients largely predominating. The diet is one rich in protein and also rich in purins. These observations have been carried out on a large scale, and the effects of the diet on the thyroid gland noted in animals in the first, second, and third generation. A full account of these observations will shortly be published. The results amply confirm my earlier observations, in showing that a rich protein diet modifies the structure of the thyroid gland. This may be shown by a marked increase in size of the gland as a whole, and by alterations in the number and arrangement of the secreting cells or vesicles of the gland. The rich protein diet at first stimulates, and later exhausts the gland. The diet can be shown to have modified the soil in a manner which increases the susceptibility to disease. Now there is no reason to doubt that under the conditions described, what is true of animals is also true of man. And I submit that conditions, for practical purposes identical to those described, are seen by us every day, that these are inducing similar - maybe less in degree - modifications of structure and function of the tissues, with corresponding modifications in susceptibility to disease. My experience of the clinical features of gout in its varied forms in the light of the results of these researches led me in 1907 to conclude that "the subjects of inherited or acquired gout have acquired from their environment, which includes diet, a type of thyroid gland which is abnormally active, and which works, so to speak, at high pressure." Further clinical experience, and the results of later investigations have in my mind confirmed and at the same time amplified this view. The amplification is of great practical importance. I have shown how the structure of the gland can be modified in animals, and more especially in young animals, by sustained feeding on a lacto-vegetarian diet (see p. 604). And I have little doubt that the beneficial effects of an exclusive milk diet, or a lacto-vegetarian diet, which we are all obtaining in certain cases every day, are largely the result of the special influence of this regimen on the thyroid gland.

Dealing with our special subject, gout, this disease is essentially a disorder of protein metabolism. In its etiology there are probably two main factors: -

(1) A particular diathesis in soil, in which, as I have already indicated, one of the distinctive features is a special type of thyroid activity.

(2) A superadded infective element. It is now some eight or nine years since I first submitted, and I think to this Society, the view that there was an infectve element in gout. That view, although based on some definite new facts in the pathology of the disease, did not then commend itself to my critics. It is of considerable interest to mention that after the short period of eight or nine years, probably more than 50 per cent, of writers on this subject in this and other countries now accept this view - which, however, is not yet fully proved. Gouty subjects are, in virtue of their diathetic tendency, specially prone to a particular type of auto-intoxication or infection, which is responsible for various gouty symptoms.

In expressing these views I am well aware of the existence of certain facts which appear at first sight to disprove it: I refer to the cases, by no means very infrequent, of gouty disorder in patients living on an almost meat-free diet, in which relief from the gouty manifestations is obtained by putting the patient on a diet which contains much animal protein and very little farinaceous foods. I have treated many such, and have made a special study of them. These are in my experience cases in which, in addition to a probable thyroid defect, there is a certain pancreatic disturbance, as can be proved by finding a pronounced pancreatic reaction in the urine. This reaction in these cases shows that there is a defect in carbohydrate metabolism, and that the pancreas is working under difficulties. If that is recognised and the patient treated accordingly, relief from symptoms will very quickly be obtained. We know, from the writings of Dr Byrom Bramwell, that there is such a condition as pancreatic infantilism; thyroid infantilism is even better known. If time had allowed I might have referred to other interesting points touching on the relationship which exists between the pancreas and thyroid.

I must, however, content myself with pointing out that the fact of the benefits undoubtedly obtained in certain cases by a relatively rich protein diet cannot be regarded as in any way antagonistic to the general view set forth in my paper.

Many interesting clinical facts can be cited bearing on the above views - some of them deal with the antagonism long recognised between tuberculosis and gout. Time will not, I fear, allow me to elaborate these. I would have liked to consider in detail the clinical effects of a judiciously selected rich protein diet in favourable cases of tuberculosis in children and young adults. The small, thin, flabby, anxmic, tuberculous-looking subject gives place to the large, muscular, high-coloured, gouty-looking individual. This is no fanciful picture. I have had under my own care weakly children with the most prominent tuberculous family history, which were treated with a rich protein diet for two years or more, and I have seen these children in later years present many of the clinical features which we associate with the gouty diathesis. A similar condition is seen in favourable cases of tuberculosis in young adults. Then as to the converse side of the picture. Consider the great muscular development, the great bodily activity, the active circulation, and the susceptible liver and skin of the gouty child. The active growth and the great muscular development are here clear indications of a more than usually active thyroid system. We know that these cases are beneficially influenced by a restriction in the amount of animal protein foods, and in later life we often see these people, of their own accord, cutting down the animal food - often considerably, and we also see them suffering from so-called gouty ailments which are beneficially influenced by the administration of small doses of thyroid gland.