Preface 



Efforts to analyze and interpret life processes, especially as they 

 relate to development, are ultimately confronted with such ques- 

 tions as: Do the orderly patterns constituting given levels of the 

 organizational hierarchy regularly arise solely as a consequence of 

 the specific interactive properties of the units comprising the next 

 lower levels? Given the proper units and the proper conditions, is 

 the spontaneous emergence of order at a higher level inevitable? 



Considerable evidence attests that, at least in some cases, these 

 questions may be answered affirmatively. Examples include the in 

 vitro aggregation of certain macromolecules, among which collagen 

 is the prototype, into fibrils of near-crystalline regularity, and the 

 selective aggregation of previously dissociated cells into recogniz- 

 able tissues. The spontaneous emergence of orderly patterns could 

 also be illustrated by examples from levels higher than the cell or 

 lower than the macromolecule. Between these levels, however, are 

 others about which information is less certain. The time is clearl\' 

 ripe to begin inquiring into the nature and origin of heterogeneous 

 aggregates of macromolecules, with special emphasis on the inter- 

 active properties of their subunits. Actually, the subunits them- 

 selves have been identified only in a few cases, and concepts of their 

 structural and functional interrelations are still based largely on 

 inference. But, as F. O. Schmitt has written, we have already 

 learned enough to "glimpse, however imperfectly, the portentous 

 possibilities now opening up before us." 



Some of these possibilities are explored in this book embodying 

 the proceedings of a symposium sponsored by the Society of Gen- 

 eral Physiologists. As the text reveals, exploration of the borderland 

 between the realms of the macromolecular chemist and the func- 

 tionally oriented electron microscopist has already yielded im- 

 portant information about the organization of living matter; it is 

 thus more than an article of faith that many biological problems 

 can be effectively attacked at this level. Not the least of these prob- 



