CELL AND PROTOPLASM CONCEPTS 



17 



and they raise the question whether ' ' filter- 

 able viruses" and "bacteriophage," which 

 seem to be panmeristic, are also vital units. 

 Furthermore, in what respect do such ele- 

 mentary vital units differ fundamentally 

 from the colloidal aggregates and enormous 

 protein molecules of chemistry? If there 

 is no really essential difference, these pan- 

 meristic units would appear to bridge the 

 gulf between the living and the non-living. 



Biologists generally hold that the sim- 

 plest and most fundamental properties of 

 life are (1) assimilation, (2) growth and 

 (3) reproduction by division; to these are 

 usually added (4) sensitivity, or the ca- 

 pacity of responding to stimuli, and (5) 

 adaptability, or the capacity of responding 

 to stimuli in a selective or differential man- 

 ner. 



"Nothing that lives is alive in every 

 part." In every organism and every cell 

 there are living and not-living portions, 

 formative and formed materials, or proto- 

 plasm and metaplasm. It is not always 

 possible to sharply distinguish these, but 

 panmerism or the ability to assimilate, 

 grow and divide is the general test of liv- 

 ing. Even in the protoplasm itself some 

 parts are more alive than others, if mea- 

 sured by their viability. The hyaloplasm 

 or ground substance remains alive even 

 after it has lost almost all of its fluid con- 

 tent or cytolymph, as is seen in dry seeds 

 and some desiccated animals. The same is 

 true of the nuclear contents; condensed 

 chromosomes have lost most of their fluid 

 content but not their ability to assimilate, 

 grow and divide. But it has not been 

 demonstrated that any of the visible parts 

 of cells, much less these ultra-microscopic 

 parts, are capable of showing these proper- 

 ties of life when they are completely iso- 

 lated from all other parts. In short the 

 entire cell is still the ultimate vital unit 

 capaMe of showing all these properties of 

 life. It seems highly probable that these 

 vital properties are the results of the com- 

 plicated interactions of different parts of 

 the cell, or, in other words, of cellular 

 organization. 



In physics and chemistry new atoms with 

 new properties are formed by new com- 



binations of protons and electrons, new 

 molecules by new combinations of atoms. 

 Perhaps in similar manner the distinctive 

 properties of life arise or "emerge" from 

 the interactions of parts which by them- 

 selves do not show these properties. This 

 principle of "emergence" is seen every- 

 where in ontogeny and phylogeny. New 

 structures and functions appear at every 

 stage in development as the result of "cre- 

 ative synthesis." It seems to me highly 

 probable that this same great principle is 

 operative in the transition from the non- 

 living to the living. If so the fundamental 

 properties of life are not found in any 

 separate individual units of protoplasm 

 but in the complicated interrelations of 

 many parts, and such individual units are 

 not independent units of life or heredity 

 though they may be factors in such com- 

 plex processes. Life is the product of or- 

 ganization and the fundamental problems 

 of biology are the organization of cells and 

 protoplasm and the interrelation of the 

 parts of this organization. 



The method of scientific analysis which 

 has been so fruitful in our study of natural 

 phenomena has led many scientists to for- ' 

 get or neglect the importance of organic 

 synthesis. Not infrequently they have f | 

 sought the properties of the whole in the 1 

 individual parts of which it is composed, i I 

 Colloidal particles and protein molecules 

 have been held to bridge the gap between 

 the living and the non-living. Chromatin 

 granules, or chromioles, have been re- 

 garded as the ultimate units of life 

 (Minchin 1915). Crystallizable viruses are / 

 supposed by some to be on the border line 

 between the living and the lifeless. At 

 present the gene is regarded by many as 

 the ultimate living unit from which all 

 other parts of the protoplasm have been 

 derived. 



This tendency to locate all the properties 

 of such a complex phenomenon as life in 

 some one or a few of its constituents is a 

 very common error. It is suggestive of the 

 ancient views as to the localization of cer- 

 tain emotions in the heart, others in the 

 kidneys or bowels, or Descartes' proposal 

 that the pineal gland is the seat of the soul. 



