PREFACE ix 



substances) from the underlying developing blastema, and (2) to 

 secrete or discharge a substance, possibly protein-enzyme in nature, 

 which contributes to the early histolysis seen in a wound before heal- 

 ing occurs. 



In an evening paper delivered to a general session of the sym- 

 posium, James Bonner, of the California Institute of Technology, pre- 

 sented an over\dew of what is currently known about essential aspects 

 of plant biology. He reviewed recent gains in knowledge about the 

 basic mechanics of plant growth and metabolism and assessed the 

 problems that still confront us. A critical question raised by Bonner 

 was: How is the use of genetic information programmed? He postulated 

 the existence of a mechanism which controls the activity of genes with- 

 in the nucleus, and then raised a series of questions about the action 

 of this presumed control system. 



On the third day of the symposium, sections concerned with more 

 specialized aspects of animal, plant, and microbial growth and plant- 

 soil relationships met simultaneously. In general, the papers delivered 

 at these sections considered growth in terms of the development of the 

 whole organism rather than growth at the molecular or cellular levels. 

 In both the plant and the plant-soil section, consideration was given 

 to problems of growth in terms of the relationship between the de- 

 veloping organism and its environment. 



The symposium ended Saturday evening with an address by An- 

 cel Keys of the University of Minnesota. Keys noted the difficulties en- 

 countered in drawing a distinction between growth and aging; he de- 

 fined both as descriptions of progressive biological changes along a 

 time axis. In a description of the relationship between aging and age- 

 related diseases, he noted that discussions of the one almost inevitablv 

 turn out to be discussions of the other. He went on to examine the rela- 

 tionship between environmental influences and factors inherent in the 

 tissues of the organism in the production of some age-related diseases, 

 particularly coronary heart disease. 



Progress in understanding so complex and enigmatic a phenom- 

 enon as growth is necessarily slow and tortuous. The subject is so vast 

 that it is being approached from many diflFerent points of view; most 

 of these were represented at the Purdue symposium. It is the hope of 

 the sponsors of the symposium that a meeting of this sort, enabling 

 workers in a variety of disciplines to come together for a mutual inter- 

 change of information, will have the eflFect of emphasizing the many 

 areas of common interest. The purpose of the symposium will have 

 been thoroughly satisfied if those attending it were enabled to derive 

 from it a sharpened sense of the ultimate unity of their subject. 



Leon E. Trachtman 



