Studies on Regulation. ceo 



The possibility of a mechanical interpretation of many of the 

 phenomena of cell life has been shown by Rhumbler in various 

 papers, and even if his application of mechanical principles should 

 prove to be too general, the importance of mechanical factors in 

 the cell must be recognized. If v^e admit the importance of 

 these factors in the cell we cannot avoid the conclusion that 

 their importance is certainly not less and probably much greater 

 m multicellular and complex structures. The rapid advances 

 of physiological chemistry have turned the attention of many 

 w^orkers away from the physical aspects of the problem of form 

 to such an extent that in some quarters attempts at mechanical 

 mterpretation of organic phenomena are accepted with more 

 or less reluctance. There can be no doubt that chemistry is 

 almost daily throwing new light upon organic phenomena but, I 

 thmk, It is no less certain that any essentially chemical theory of 

 form must be incomplete. One reason for the somewhat helpless 

 attitude of certain authors before the problem of form is, I am 

 convinced, due to their failure to recognize the importance of 

 physical as opposed to chemical factors. We may recognize the 

 importance of these factors without making of them a universal 

 principle of interpretation. All the present and future resources 

 of both chemistry and physics are necessary for the interpretation 

 of biological phenomena, but especially in connection with the 

 problem of form in which masses and mass-relations are an 

 important element are mechanical principles of interpretation 

 of value. 



Roux has pointed out the importance of mechanical conditions 

 as functional stimuli, and hence, according to his view, as forma- 

 tive factors in the case of various organs whose function is wholly 

 or in part mechanical. But we must admit that mechanical con- 

 ditions as stimuli exert in many cases not only a more or less com- 

 plex physiological influence but produce a direct mechanical eff"ect 

 and that this effect under typical conditions is typical. The 

 change of form in pieces of Stenostoma (Child, '02, '03) in conse- 

 quence of mechanical tension and the asymmetrical form of pieces 

 of Lepto plana (Child, '04a) resulting from changes in the direction 

 of locomotion are cases in point. No one would be more ready 



