THE ORGANIC CELL 
85 
logically, however, the single cell cannot be looked upon as an 
independent unit, for its very existence depends on the general 
life of the organism. 
Schwann many years ago stated that ‘ the whole organism 
subsists only by means of the reciprocal action of the single 
elementary parts.’ Schwann erred to a certain extent in this 
statement, for he denied the influence of the whole organism 
upon the functional activities of the individual cell. 
The cells must be looked upon as centres of a formative 
power, affecting and influencing the growing mass as a whole ; 
the idea of a physiological independence of the individual 
cell must recede into the background. The life of the multi- 
cellular organism must be looked upon as a whole, its composite 
character being the result of a secondary distribution of energy 
among local centres. Looked at in this light it will be necessary 
to discover the means by which the single cell comes into 
relation with the whole organism. Tissue cells often appear 
isolated from their neighbours on account of the non-living 
walls separating them ; one must not, however, conclude, from 
this apparent isolation, that an actual solution of organic 
continuity has been established. For instance, there are many 
cases in which a nucleus may divide, but the cell -body does not 
share in the process, so that multinuclear cells come to be 
formed which consist of a uniform and continuous mass of 
protoplasm, studded in the substance of which are nuclei, the 
whole mass forming a colony of cells connected by cell-bridges 
by which free communication can be maintained. Years ago 
the contention was maintained by Heitzmann that in nearly all 
forms of tissue the process of division is incomplete, and that 
though cell-walls may be formed, these walls do not form 
barriers to communication between adjacent cells, because 
these cell-walls are penetrated by strands of protoplasm by 
which organic continuity is established in the mass. 
He therefore looked upon the body as a highly proto- 
plasmatic reticulum, the cells being nodal points in the network, 
the essential factor of the conception being the protoplasmic 
continuity of the whole. 
It has long been known that cell-bridges exist between the 
sieve-tubes of plants. A. Meyer has shown that in plant- 
