ABSTRACT
Among the myriads of bodies in the world there is one great class whose individuals are able to perform a considerable number of acts upon which their continued existence depends. One great subclass of living bodies has greater ability for acting than another subclass. This chapter presents an overview of the key concepts discussed in this book. The book begins with the common heritage of man and brutes, but carries the comparison throughout the range of his endowments and activities, to examine closely wherein he differs from the brutes. The base line for the comparison is found in the unique ability of living things as compared with all other things to fit themselves into different environments. This ability is known as adaptation and is widely recognized in the treatment of man and all other organisms. The ordinary knowledge of life contains the idea of adaptation in both structure and activity as essential to life.
