This monograph is a summary of the work on tissue cultures. The introductory chapters consider briefly the development of these studies. Then follows an account of the culture medium and the preparation of cultures for microscopic examination. Other chapters give methods for obtaining pure cultures of tissues; the use of tissue cultures for observing the effects of the body fluids; the interaction of various tissue cells in vitro and in morphogenetics. The final chapter considers tissue culture as a means for studying pathologic changes, immunity, the interaction of bacteria and tissues, cytotoxins and finally tumors.