322 STUDIES IN GENERAL 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. Weare, 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 of 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. 
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