CHAPTER V 



TISSUE CULTURE 



The cell is the ultimate seat of all vital processes, but these 

 processes do not depend on the activities of one cell alone, for the 

 multicellular organism is a united, harmonious whole. This 

 means that happenings in higher organisms are the expression of 

 the correlated behavior of many cells, each dependent upon the 

 other and upon their environment. These truths are the working 

 hypothesis and the philosophy of the "new cytology." The old 

 cytology dealt primarily with the individual cell considered 

 apart from its environment. The new cytology has to do with 

 the relationship between the living cell and its neighbors near and 

 far and the fluids which bathe them all. 



The study of dead (fixed and stained) material has revealed 

 much of value. The series of events involved in cell division — 

 indeed, the very existence of the chromosomes and many similar 

 details in cell anatomy — were first made known through the 

 study of killed tissues. But such studies, important as they are, 

 have had to do mostly with the form and structure of cells, often 

 neglecting function. Structure is of significance only in so far 

 as it explains function. 



The German physiologist Schwann, one of the authors of the 

 cell theory (1839), called attention to the importance of body 

 fluids in the life of the cell, but cytologists continued to center 

 their attention on anatomy, until the French physiologist Claude 

 Bernard (1878) again pointed to the necessity of considering the 

 medium in which cells are bathed. One of the modern advocates 

 of this point of view is the French-American experimental sur- 

 geon Alexis Carrel, who has repeatedly emphasized that cells are 

 in physiological continuity with their environment and that only 

 with their environment do they constitute a whole. 



The living cells of tissues can rarely be studied within the body 

 and therefore within their natural environment. The cell 

 physiologist was, therefore, confronted with the task of dupli- 

 es 



