Autolysis is a rigidly controlled process; it is no blind, undirected bull-in-a-china-shop affair. Not only throughout the fasting period, but also throughout the starvation process, as well, the body exercises control over autolysis. The most rigid economy is exercised throughout both periods in the digestion and utilization, not of the vital and most vital tissues, but of the dispensable and expendable tissues. In a later chapter we shall study the control of the autolytic process during fasting. Here I wish to call attention to the fact that in starvation there is no indiscriminate wasting of the body, but rather the same safeguarding of the more vital tissues and a slow sacrifice of the less vital tissues that is seen in the fasting period.

When the frog fasts during the time it is consuming its tail, only the tail disappears. Never does one of the legs of the frog undergo autolytic disintegration. No needed structure is digested and absorbed. If planaria, or flat worms, are cut into small pieces and placed where they can absorb nourishment, each piece will grow into a small worm. If they cannot get nourishment, they cannot grow. Each piece, therefore, completely re-arranges its materials and becomes a perfect, but very minute worm. The piece that contains the pharynx, finding this too large for its diminished size, will dissolve it and make a new one that fits its new size. We have here a process similar to the metamorphosis of insects that goes on in the pupal stage. Here is manifest the ability to tear down a part and shift its constituent materials. The same thing is seen in the softening and absorption of the bone-ring support around a point of fracture. Only part of the bone-ring is digested, the remainder is retained to reinforce the weakened structure.

Zoethout and Tuttle point out that autolysis is a controlled process and mention the following examples of carefully controlled autolysis that normally occur at certain periods of life: "atrophy of the mammary glands at the close of lactation, of the uterus after parturition, the general atrophy of old age, and the resolution (dissolution) of the exudate formed in the lungs during pneumonia." The atrophy of the thymus gland at puberty should also be included in this list.

These authors offer other examples of controlled autolysis, saying: "During starvation some organs (heart and brain) are absolutely necessary and their activity cannot be dispensed with; hence they must be supplied with proteins. These proteins are obtained from the skeletal muscles, which must be looked upon not only as organs of contraction but also as storehouses for proteins. The proteins of the muscles and other organs are digested by the intracellular proteases (enzymes) into soluble proteins, amino acids, which are then carried by the blood stream to the vital organs. Another striking illustration of the transfer of protein from one organ to another is seen in the tremendous development, in the spawning and fasting salmon, of the ovaries at the expense of the muscles, which lose as much as 30 per cent of their weight."

Neither the ovaries, nor the heart, nor the brain can live, grow and function on a diet of amino acids. They need minerals, carbohydrates, fats and vitamins. Fasting salmon lose more than weight of muscle; they also lose fat and glycogen. There is a great accumulation of phosphorus in the gonads of fasting salmon.

It is interesting to note that this control of autolysis extends also to pathological tissues, such as tumors, deposits, effusions, etc. and is not confined to the normal tissues of the body. Examples of this will be given later.

The fact that autolysis is a rigidly controlled and not a haphazard process, is our guarantee that the vital tissues of the body will not be sacrificed during even prolonged abstinence from food. It guarantees us that only the non-vital tissues will be digested and their constituents carried throughout the body to nourish the vital tissues.

Three important facts stand out clearly in what has gone before:

1. By reason of its possession of intracellular enzymes the body is capable of digesting its own proteins, fats and carbohydrates.

2. It is fully capable of controlling the self-digesting process and rigidly limits it to the non-essential and less essential tissues. Even in starvation, when vital tissues are destroyed, there is rigid control of the process and the tissues continue to be drawn upon according to their relative importance.

3. The body is capable of utilizing the end-products of autolytic disintegration of its own tissues to nourish its most vital and most essential parts.