322 STUDIES IN GENEBAL PHYSIOLOGY 



A piece without the nucleus "cannot develop into the 

 form characteristic of the species, and growth does not 

 take place." Yet a piece without the nucleus, as Nuss- 

 baum found, can move for a long time ; nuclear substance 

 is, therefore, not necessary for "activity" or "spontaneity." 

 Nussbaum draws the following conclusions from his ex- 

 periments: 



(1) Nucleus and protoplasm can live only when united; isolated 

 they die after a longer or shorter time. (2) For the maintenance of 

 the morphogenetic energy of a cell the nucleus is indispensable. 

 (3) Each of the energies produced by a cell depends upon a sub- 

 stratum that can be divided. 



If I understand Nussbaum correctly, the latter statement 

 means that a part of the nucleus and of the protoplasm 

 is sufficient to render possible all the life-phenomena of 

 the cell. 



Finally, I wish to quote also the following from the 

 work of Nussbaum: 



The cell is not the ultimate physiologic unit, even though it 

 must remain such for the morphologist. We are, however, not able to 

 tell how far the divisibility of a cell goes, and how we can determine 

 the limit theoretically. Yet for the present it will be well not to 

 apply to living matter the conceptions of atom and molecule, which 

 are well defined in physics and chemistry. The notion micella 

 introduced by Nageli might also lead to difficulties, as the prop- 

 erties of living matter are based upon both nucleus and proto- 

 plasm The cell consequently represents a multiple of 



individuals. (P. 522.) 



The conception which we must therefore form of the 

 nature of the simplest elements of living matter capable 

 of development is this, that it consists of a system pf at 

 least two different substances, of which the one is con- 

 tained only in the nucleus and the other only in the proto- 

 plasm. The experiments of Nussbaum have been repeated 

 and amplified by a large number of careful observers. 



