A point of great importance too little emphasised by dietetic reformers is the undoubted existence in certain individuals of idiosyncrasy for certain articles of diet. Nothing more fully illustrates the truth of the old proverb, "What is one man's food is another man's poison." Manifold instances are recorded of people who could not eat fish, shell-fish, strawberries, honey, sugar, apples, eggs, meat, rice, figs, pears, and even wheat, without presenting disagreeable symptoms, which in more than one case where there was a hereditary predisposition have terminated in death.

In my opinion this constitutional peculiarity accounts for the origin of many of the cults. Trousseau somewhere has said that medical men are in the habit of prescribing for their patients that kind of food which best suits their own individual cases, and I am inclined to think that dietetic theories are often propounded by those whose metabolism is imperfect. The chemical physiology of digestion has claimed so much attention from observers that they have had little time to devote to the chemical pathology of indigestion. It is not sufficient to make a classification of the various enzymes in the alimentary canal and align them against the respective food-stuffs which they are known to attack. Digestion is more than mere chemical solution. It is doubtless true this is the first stage, but probably only because of the necessity to prepare for the future co-operation of bacteria. The perversions of metabolism will never be fully understood until a careful study has been made of the end-products which exist in those who depart from the standard of health. We shall thus see both sides of the shield and be better able to estimate the true role of food in health as well as in disease. It may well be that, given a perfect knowledge of diet - the appropriate building material of the body - we may not only cure but actually eradicate disease, and thus fulfil the ideal function of the medical profession. The problem as to how best to increase the efficiency of the individual and the race is ever in the foreground of the best minds of the medical profession. Preventive medicine has already abundantly justified its existence by suggesting practical solutions of this problem, and we cherish the fondest hope that when we have accurately fitted the dietary habits to the true physiological requirements of the body we shall have provided a most potent factor in the struggle for health, strength, increased working capacity, and the possession of increased powers of resistance to disease.

I am indebted to a medical friend for the following very apt simile of the present relations of the medical profession with the public. He compares the doctors to a company of first-aid experts eagerly desirous of helping the community, and stationing themselves, fully equipped with the latest additions to the resources of their art, at the foot of a precipice where they may practise on any who are unwary enough to tumble over. Their true function, he avers, is to erect a powerful fence at the top of the precipice, which will effectually prevent such catastrophes and so remove the necessity for all the elaborate preparations at the foot. He is, of course, presupposing that the only hindrances on the road to ill-health are of a preventive and - he is inclined to believe - mainly of a dietetic origin, and that a perfect knowledge of the most suitable alimentary substances and the rules of health duly applied would eliminate disease. One can hardly assent to a proposition so restricted in its character, and it is perfectly certain that even if we were to take it for granted, the individual can hardly be ministered to in any other manner than that which obtains at present. But it is to the everlasting credit of the medical profession that not only has it emphasised the necessity for some such preventive policy, so far as it is possible without unduly interfering with the liberty of the subject (and in this way done its very best to nullify its own existence as at present organised), but its warning voice is raised without cessation in the interests of personal health.

The question of variety in diet is one of profound importance. It is a matter of common observation that those who confine themselves to a monotonous diet, even although it is capable of satisfying the full caloric necessities of the body, are apt to lose weight and exhibit an ill-nourished appearance. This is more particularly noticeable when the feeding of one day is practically a replica of that on preceding days, and probably owes its origin to the fact that the alimentary canal, and for that matter the senses, do not receive a sufficient amount of stimulation, and therefore are not aroused into activitv commensurate with extracting all the nutriment from the food. Pleasures of all kinds are apt to pall, and even agreeable dishes with the most pleasing of flavours soon cease to be regarded with acceptance, and lose their power of titillating the palate and nasal mucous membrane when they appear at meal times with unfailing regularity. The aesthetic susceptibilities are offended, and the appetite juice reduced to a minimum. It is a trite saying that "hunger is the best sauce," but probably monotony of diet is the only justification for the use of any kind of sauce. Yet it is a remarkable fact that even a fresh method of preparing the same kind of food makes an indubitable appeal to the appetite and is followed by a more thorough utilisation of the food.

Apart altogether from this psychical or reflex influence, there is another aspect of the question deserving of equal consideration. In all probability the most potent advantage of a mixed diet of animal and vegetable origin is the conviction that we are thereby assured of the inclusion of the varied elements essential to the formation of a well-balanced dietary. Restriction of the daily menu tends to deprive the body of ingredients absolutely indispensable to its welfare, as is well exemplified in the case of beri-beri. The importance of mineral salts to the economy is receiving due emphasis to-day, not only with reference to the actual quantity required, but likewise of the ratio of the various salts to the protein, carbohydrate, and fat of the diet.

We have thus concluded what does not pretend to be an exhaustive consideration, but only lays claim to be a fairly comprehensive survey of the most modern theories of dietetic practice. It includes all those theories which have engaged the attention of medical men and laymen for many years, but excludes many which have merely an individual application and ought to be classed as purely speculative rather than expository. Amongst such I can prominently recall the extraordinary practice of a medical man who was accustomed to insist that the stomach could deal with any kind of food, provided it was required to give attention to only one article at a time, and supported his belief by confining himself to the consumption of one single article at each meal. The astonishing circumstance was that he professed himself perfectly satisfied whether his two meals a day consisted solely of potatoes for lunch and milk for dinner or beef for the former and fish for the latter, but his premature decease from a mental ailment was probably a sufficient explanation of his erratic practice.

I do not doubt that most of the systems detailed may be made to answer the nutritive and dietetic requirements of everyday life for individual cases, and, as has been proved by experience, some of them may even be suitable for considerable sections of people. I do not think, however, that any one of them has succeeded in demonstrating its right to the proud position of the universal food of mankind in the temperate zone. I am personally inclined to favour the claims of the low-protein system as on the whole the most satisfactory solution of the dietetic problem, but probably more reflective people will acquiesce in the proposition that the healthy man can live on any system of diet by attention to moderation, regularity, and variety, but the unhealthy man must look to the dietetic expert to guide him in the selection! of the best system or kinds of food to suit his case.