In considering the values of foods and the quantities required, and in apportioning these into special diets, it will be convenient to treat of diets according as they are required for ordinary conditions of life, for special training and exercise, or for the treatment of slight departures from normal health, such as obesity and some minor alterations of function.

We have already seen in chapter i. that the body weight in pounds, multiplied by 9, gives the minimum amount of albumens required for a sedentary life, and by 10 or 10.5 those required for an active life, such as that of an out-door labourer.

And if we take an active man of 140 lbs., and apply these rules, we find that he will require 1,400 grains of albumen per day, which will produce about 466 grains of urea per day when completely digested and metabolised.

With regard to urea, I may say that the percentages of albumen values, to be given in the diet tables that follow, have been found by me from practical trial to be very close to the truth; for though on a weighed diet, continued from day to day, urea will be one day below and another above the quantity calculated from the albumen values of those foods, when taken over days or weeks, these fluctuations tend to balance each other, and over such a period the urea calculated from the albumens generally comes very close indeed to the urea found.

These fluctuations no doubt arise from variations in the time of digestion of the foods used, as the digestion and absorption of a food taken one day is not necessarily concluded in time for the twenty-four hours' division of the urine; and then, again, when albumens have been absorbed, they may, as we have seen reason to believe, remain either in the blood or the tissues as a reserve of force, till a special call for force production and activity is made (see fig. 1 and remarks upon it; also "Uric Acid," p. 335).

But when allowance is made for these causes of variation, the values to be given are, I believe, quite sufficiently accurate for our practical purposes.

Now the albumens required for this man of 140 lbs. can be got from:-

Table I

10 ozs. of bread

8 per cent. of albumens

= 340 grs.

2 ozs. of oatmeal

12

= 104 „

2 pints of milk

3 " "

= 525 „

1 1/2 ozs. of cheese

33 " "

= 210 „

1 oz. of nuts

16 ,, ,,

= 68 „

18 ozs. fruit and vegetables, say 1/2 to 2 ,, ,,

= 153 „

1,400

Now it is obvious that such a diet list may be varied greatly in very many directions, and that such variations may be used as temporary changes or permanent diets, according to taste, habits, cost, facility for preparation, and other concomitant conditions.

For those who do not do well on or like much fluid, the milk can be reduced to 1 pint per day if the cheese is increased to 3 1/2 oz.; others again may be able to increase bread or bread stuffs to 16 ozs., which would just about enable them to reduce the milk to 1 pint or cut out the cheese entirely, and some may take still more bread up to 24 ozs.

Those who do not like or cannot digest nuts in any form or of any kind, may leave them out, slightly increasing the bread, milk or cheese, or replacing them by about three times their quantity (3 oz.) of dried fruit.

I will just mention that almonds are to be obtained at all times, that well roasted and salted they are generally liked, and that for those whose teeth are not of the best they may be passed through a nut-mill.

Nuts have the further advantage common to many substances that leave undigested residues of tending to prevent or relieve constipation; in other people, however, they again, in common with other undigested particles, may cause some intestinal irritation, which may give rise to papular and other slight skin eruptions.

And I would here refer to what I have already said about indigestible substances on p. 16, for in some people nuts may relieve dyspepsia by putting an end to the constipation to which it was due; on the other hand, if given to people who have suffered from gouty or other intestinal irritation with or without diarrhoea, they may increase the irritation and intensify its evil effects, such as malnutrition and anaemia, and pave the way for still more terrible enemies such as tubercle.

In every change of diet, then, we must see that the new food is sufficient in quantity and satisfactorily digested by the individual in question; and this can only be done by making diet alterations very slowly, one meal at a time, and watching and testing the digestibility of each new food stuff as it comes to be used.

For this purpose I am in the habit of advising that only one meal should be altered at a time, and that each meal should be watched for, say 7, 10 or 14 days, and regarded as quite satisfactory both as to quantity, quality, digestibility, resulting strength and power for work, before the next meal is taken in hand.

And where difficulties are met with, one food after another should be tried and tested till the best results are obtained, and no matter how slowly they have to go, beginners must always refuse to move the second foot till the first is firmly planted.

In cases where it is of extreme importance that there shall be no failure of strength and nutrition on the new diet, as for instance where there is either tubercle in the family, or its onset appears to threaten the individual in question, it is well to take the precaution of estimating the urea for a few days on the old ordinary diet, and then to supply albumens on the new diet in accordance with the results obtained.

Thus if the average excretion of urea on 4, 5, or 6 days either consecutive or taken at random is 450 grains, then we must supply 450 X 3=1350 grs. of albumen per day on the new diet; but if the patient has had a bad appetite on the old diet, so that the average urea is below the physiological level of 3 or 3.5 grs. per pound of body weight per day, then we must go by the body weight, giving a physiological allowance of urea and albumen, and not by the urea found.

But if tubercle is actually present, and feeding up is indicated, then far more than the physiological allowance of albumens should be given, and the patient can be stuffed with food to any extent that is possible, as 4 pints of milk, 16 ozs. bread stuffs and 4 ozs. of cheese in many shapes and forms, with butter and cream ad lib.; and it is certainly no harder to overfeed a patient on this diet than on one of flesh, indeed it is often much easier, and as I have said in "Uric Acid" (p. 393) much less dangerous.