At the very commencement of life autolysis is an essential process. The embryonic development of animals in eggs involves digestion of the food stored in the eggs. Eggs, however large or small, contain a living germ that is microscopic in size which is the only living part of the egg. The remainder of the egg consists of stored food material out of which the evolving animal constructs its organs and parts. This food substance is no more suited to the use of the evolving embryo than it is suited to the use of the adult animal. Before it can be used in making tissue, it must be digested. This digestion is achieved by enzymes produced by the embryo.

The fasting salamander, the tail of which has been cut off, grows a new tail. It draws upon its general food stores for materials out of which to construct the new tail. These materials must first be broken down (digested) by the process of autolysis and then transferred to the growing tail. Here we watch a process that is somewhat the reverse of that seen in the frog that is absorbing its tail. Here materials are taken from the body and used in producing a tail; there materials are taken from the tail and used with which to nourish the body.

The enormous growth of the gonads of fasting salmon is accomplished by transferring materials from the body of the salmon to the testicles. Autolysis is necessarily the first step in this transfer of materials.

The body is not only able to build tissue, it can also destroy tissue. It can not only digest and utilize the tissues of other organisms, it can digest and use its own tissue.