There is not in the whole realm of Nature a perfect example of the diversification of function under one indivisible whole to equal that shown by the digestive tract of man or the lower animals.

We have wonderful machines today that take the crude material, process it, manufacture it into forms and label it, all in one process, and we think this marvelous, but as compared with a man's digestive machinery this is a mere toy.

We take crude materials into the mouth, we chew these and mix them with saliva containing a ferment that starts the digestion at once, this continuing down through the entire tube to its final receptacle, the colon.

Not only is food converted into products that can be utilised by the body, but by an intelligence resident in the cells lining this tract certain things are selected out of the mass of chyme and these further elaborated in the blood stream, thus continuing the process of digestion in the body itself till all the needs have been met, and we are fed.

Each separate division of the digestive tract has its own peculiar function to perform, its own particular addition to make to the total of the task, and no one division can do the work for any other division.

The food absorbed and finally prepared in the blood and lymph stream for use, becomes brain, muscle, nerves, glands, eliminative organs, fat, or some other part, or it is again turned into matter to be eliminated from the body, if not required there.

If the digestion is of starchy or sweet foods there is an entirely different process in use than is the case when the protein foods are under digestion.

Thus, we take into the mouth bread or cereal food or potato, we chew this thoroughly, not only to comminute it finely, but more particularly to mix it intimately with the saliva, where it is acted on by the ptyalin, a ferment or enzyme whose one function is the preparation of this class of foods for more complete digestion in the small intestine, and without which preparation the further digestion is certain to be incomplete, and accompanied by much fermentation.

Starches and sugars, the so-called carbohydrate group of foods, require alkalin conditions throughout for complete digestion without fermentation, acid introduced with these insuring arrest of digestion, when, in the presence of heat and moisture, an alcoholic fermentation sets in almost at once.

If the chewing and insalivation have both been complete and thorough this bolus of partly converted starch enters the stomach through the aesophagus, or swallowing tube, and there, if no acid interferes, this conversion to lower forms, or splitting of the starch, goes on till it reaches the condition of a secondary sugar, or a dextrose.

If, however, acid fruit has been taken at the same time this reduction will be arrested, for the conversion or splitting of starches by the ptyalin can occur in nothing but an alkalin medium. The reader is asked to remember this fact, for it will be referred to frequently later.

But if no acid occurs to interrupt this digestion or splitting process, it continues till the stage of dextrose is quite fully reached, when it begins to filter out into the duodenum, the next division of the digestive tract, and here again the reaction is alkalin, so the process continues, the action of the enzymes from the pancreas still further reducing the carbohydrate till it reaches finally the stage of primary sugar, or glucose.

In this stage of preparation it is absorbed by the villi of the small intestine, the first division of this below the duodenum being called the jejunum, and from the small intestine is passed to the liver.

The liver is the great filter which stands between the intestinal tube and the general circulation, and it is the business of this great gland to inspect and pass judgment on everything absorbed from the small intestine and the colon.

If the absorbed nourishment can pass this censor, it is admitted to the general circulation; if not, it is then passed out through the bile ducts into the duodenum, and down to the small intestine where it again goes through the same process till all has been finally accepted by the liver or finally rejected, in which case it passes to the colon where it is stored for dejection at some convenient time, and so leaves the body.

If the result of starchy or sugar digestion, in the form of glucose, finally reaches the general circulation, it meets there an enzyme or ferment from the tip of the pancreas, the little ductless end of this very important gland, whose function it is to complete the conversion of the carbon material to fuel for the machine, glycogen, and in this form it is carried in the blood or stored in the tissues, in the muscles, in the interstices of the liver, in the cellular tissues where it will be ready when called for by muscular exercise.

Now, here is where diabetes mellitus comes in, for the diabetic is one who cannot furnish this ferment in sufficient quantity to convert fully this dextrose to glycogen, so that the tissues feel the need for their accustomed fuel (weakness) or the dextrose is carried in the blood beyond the blood's ability to take care of it. It is thrown off, still in the form of dextrose and we recognise it as sugar in the urine.

This is the completed cycle of starchy or sugar digestion, and you can see how important it must be not to interrupt this cycle at any stage by introducing either an acid fruit or other form of acid.

If the ingested material should happen to be meat, eggs, or fish, the animal forms of concentrated protein, then there is an entirely different process.

There is nothing for the saliva to do in the digestion of this class of foods, as witness the quick bolting of meat by the dog or other meat-eating animal, so chewing in this class is of no importance at all, throwing some doubt into the mind as to whether a mouth equipped with such complete mechanism as is necessary for taking care of the complex starches and sugars is really intended by Nature to take care also of the concentrated forms of protein.