r 8 82.] The New Factor in Organic Development . 285 
of effecting simultaneously suitable variations in all the 
organs concerned. 
This simultaneous action, perhaps, in millions of parts 
must be considered as its characteristic in contradiction to 
the modus operandi of selection, which can develop only a 
very few properties at once. The question of heredity, upon 
which Dr. Roux throws a new light, must be for the present 
passed over in silence that we may proceed to the main 
subject — the conflict of parts in the organism. It must be 
remembered that even in the highest animals centralisation 
is not so complete as is popularly supposed. The foundation 
of the conflict of parts is their inequality; hence arises a 
struggle in consequence of growth and of the transformation 
of matter. It will be understood that each unity can come 
into collision only with unities of the same order. There 
can be no conflict between a cell and, e.g. f an organ. 
Passing over the struggles of the molecules, the cells, and 
the tissues we may find this principle of conflict or competi- 
tion most clearly shown in the organs. We find here 
heterogeneous parts contending for two requisites — room 
and nourishment. As a consequence it follows that only 
those combinations of organs can subsist in which parts 
chemically and physiologically non-equivalent can yet 
maintain a morphological equilibrium. For if one part were 
so successfull so powerful in its growth as quite to suppress 
the others, the whole must perish. 
Though the inter-aCtion of the organs has long been 
known and studied, it has not been viewed as a selective 
struggle for space. The mutual limitation of the intestines, 
especially the passive dependence of the shape of the liver, 
was noticed even by Vesalius. Rott has shown that in 
cases where the right kidney is wanting the normal depres- 
sion corresponding to this organ is absent. The lungs 
depend in their size and form on the heart, the shape of the 
thoracic cavity, the diaphragm, &c. The cerebral hemi- 
spheres flatten the cerebellum. Muscles, e.g,, those of the 
calf, likewise flatten each other. This mutual conflict: has 
led to the utmost utilisation of the available space. An in- 
crease of any organ is possible only at the expense of some 
other organ unless the latter has the power to resist its 
encroachments and compel it to grow merely in an outward 
direction. It must be noted that organs rarely if at all used 
may maintain themselves for a long time in places where 
they are exposed to no competition for space, as in the ear- 
muscles of man. 
Dr. Roux is of opinion that this direCt conflict of the 
organs for space will furnish a better explanation of many 
