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Proceedings of the Boyal Society 
essays* discussed inductively, it is the object of the present paper to 
apply the modern conception of protoplasmic anabolism and katabolism 
to the phenomena of growth, reproduction, sex, and heredity. At dif- 
ferent levels of analysis, attempts have indeed been made to rationalise 
these phenomena, the theories of sex alone being said to number hun- 
dreds, hut it has been already pointed out that an interpretation of func- 
tion in terms of protoplasmic changes is, in its nature at least, ultimate. 
§ 1. Growth . — The first adequate discussion of growth is due to 
Spencer,f who pointed out that in the growth of similarly shaped 
bodies, the mass increases as the cube of the dimensions, the surface 
only as the square. Thus in the growing cell the nutritive 
necessities of the increasing mass are ever less adequately supplied 
by the less rapidly increasing absorbing surface. The early excess 
of repair over waste secures the growth of the cell, but the neces- 
diagram. Protoplasm is regarded as an exceedingly complex and unstable 
compound, undergoing continual molecular change or metabolism. On the one 
hand, more or less simple 
dead matter or food passes 
into life by a series of assimi- 
lative, ascending changes, 
with each of which it becomes 
molecularly more complex 
and unstable. On the other 
hand, the resulting proto- 
plasm is continually breaking 
down into more and more 
simple compounds, and finally 
into waste products. The 
ascending, synthetic, con- 
structive series of changes are 
termed “anabolic,” and the 
descending, disruptic series, 
“ katabolic.” Both processes 
may be manifold, and the 
predominance of a particular 
series of anabolic or katabolic 
changes implies the specialisa- 
tion of the cell. The upper figure (A) represents the complex unstable protoplasm 
as if occupying the summit of a double flight of steps ; it is formed up the 
anabolic steps, it breaks up and descends by the katabolic. The lower figure (B) 
is a projection of the upper, its convergent and divergent lines serving to repre- 
sent the various special lines of anabolism and katabolism respectively, and the 
definite component substances (“ anastates ” and “ katastates ”) which it is the 
task of the chemical physiologist to isolate and interpret. 
* “ Reproduction” and “Sex,” Ency. Brit., vols. xx. and xxi. 
t Principles of Biology. 
