If at any time there is a doubt on the matter the urine of 24 hours should be collected and the urea estimated to make certain.

Given sufficient albumens, it is a matter of very little consequence where they come from, whether from the animal or vegetable kingdom, though, of course, where poisons are swallowed with the albumens, these will influence the results, as we shall see further on; but the first point is, a sufficient quantity of albumen, and this in a condition suitable for digestion and absorption.

With these simple facts kept ever in mind there is no difficulty at all in getting sufficient albumen, and therefore sufficient strength and nutrition, out of many kinds of food besides those which form the staple diet of England to-day.

But those who have been ignorant of these facts, and have attempted to walk without the light of knowledge, have fallen into many and great errors, but chiefly in one of two directions.

Either they have been ignorant of the quantities required, and have greatly over-estimated the nutrition values of garden vegetables and garden fruits, attempting to live on these alone, which it is almost impossible to do. Or they have underestimated the nutrition values of such things as milk and cheese, and attempted to eat them in as large quantities as the above fruits and vegetables.

It is also possible, by introducing more food than can readily be digested, to overpower digestion, so that nothing is digested and absorbed, and starvation results, a fact which is brought to the front in the most interesting manner in the writings of Dr. Dewey.1

Effects of milk on the excretion of urea.

Fig. 2. - Effects of milk on the excretion of urea.

1 "The True Science of Living," by E. H. Dewey, M.D., Norwich, Conn. The Henry Bill Publishing Company, and J. and J. Bumpus, Ltd., Oxford Street, London, England. 1895.

We learn then from fig. 1 that as supplies run short, urea and the power of force production fall lower and lower, but that a supply of food does when digested, and generally in the course of thirty to ninety minutes, introduce into the blood a fresh supply of albumens available for the production of force and urea, and then up goes the urea curve, and the power of producing force is correspondingly increased.

And this is a very simple experiment which any one can repeat on, in and for, themselves.

Fig. 2 shows the effect of a similar fast to that of fig. 1, broken in the thirteenth hour after 8 p.m., by the taking of 1/2 pint of milk.

Here in the hour ending 8 a.m., urea is at 12 grains per hour and it rises at 9.0 above 18 grains and gradually falls from that on till 1 p.m., when it is about 13 grains per hour. Now if we take it that urea, if no food had been taken, would have gradually fallen from 12 grains per hour to 9.5 grains per hour at 1 p.m. and draw an imaginary line accordingly, the urea enclosed between these two lines will equal that produced in five hours from the albumens of milk taken, and this is about 28 grains or almost exactly 2/3 of the calculated urea value of 1/2 pint of milk, and probably the rest would have been obtained, only longer time was necessary for it to come out. Similarly with cheese and other foods their urea value to some extent comes out in five hours following ingestion, and thus roughly the nutrition value and digestibility of many foods may be directly tested on any individual about whom the information may be required.

Thus fig. 3 shows the effect of taking at 8.15 a.m. 1 oz. of cheese. Here we see that in contrast with what happened with milk, it is only in the second hour after the cheese that we get a rise of urea.

Then considering that urea would have fallen much as in the other figures, if no cheese had been taken, we get urea enclosed between the two lines equal to 17.7, say 18 grains, and this multiplied by 3 is equal to 54 grains of albumen.

But this cheese is theoretically equivalent to 140 grains of albumen, so that in five hours of digestion we have got less than half its urea and albumen value.

This looks as if cheese is both harder and slower of digestion than milk, and is probably after all less completely digested and leaves greater undigested residues.

I must say, however, that the cheese taken was Gruyere, and it was somewhat hard from keeping, which probably accounts for part of its slow digestion and indigestibility; still I give the result to show how the probable nutrition value of foods may be gauged by this process.

Many people say that they cannot digest milk or cheese; but a few tests similar to these would soon show whether there was any truth in the statement.

Effects of cheese on the excretion of urea.

Fig. 3. - Effects of cheese on the excretion of urea.

A similar test may be applied to such foods as nuts, Protene, Plasmon and gluten, to be mentioned further on. And all these dry or hard albumens are, in my experience, more slowly digested than cheese, just as one would expect, and for the same reason, as we see, cheese is more slowly digested than milk.

People vary considerably in their powers of digesting these things, and while some will produce urea from them equal to at least 3/4 of their calculated value, others will produce much less down to less than half their value, and others again appear not to digest them at all, there being no rise of urea whatever.

Things which increase appetite and digestive power appear to increase the urea that is obtained from these dried forms of albumen, and thus some people can digest these foods when leading an active life, and not when sedentary.

The time at which they are taken and their admixture with other foods make also important differences in the results obtained, and I mention these things here to bring out the value of the above test, for the quantity of urea produced from any food in a given time is an absolute guide to the nutrition value of that food for the individual on whom we are working; and by this test milk stands quite at the head of the list, and is followed by cheese, and some way behind this by the above and other forms of hard or desiccated albumens.