Introduction

Abstract

The period of the 1940s and 1950s marked a turning point in the study of regeneration. Until then biologists working on the study of regeneration had conducted their researches on various invertebrates and lower vertebrates, During this period, however, experiments also began to be performed on mammals. Before such a radical change in the direction of research could take place, certain preliminary requirements had to be fulfilled. In fact, the switch to the study of regeneration in mammals was preceded by a theoretical demonstration of its possibility. The course of regeneration in mammals has been studied by physicians since ancient times. However, they studied it from a particular standpoint and quite apart from the study of regeneration in other animals, and as a result the results obtained by the study of mammals were regarded as something quite distinct from all other branches of the. science of regeneration. Nearly all investigators assumed that in mammals and man regeneration can be manifested in only two ways: the healing of wounds and a slight degree of regeneration of tissues. The capacity for both types of regeneration is extremely slight and it cannot be compared with the regenerative capacity of animals usually used as test objects by biologists. As regards the healing of wounds such a conclusion is justified, for this term essentially implies the absence of regeneration and its replacement by an adaptation to protect the internal tissues from harmful environmental action. In mammals, for instance, the limbs do not regenerate and wounds simply heal at the site of injury.