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THE PRINCIPLES OF BIOLOGY. 
and less specialized parts are more capable of performing 
vicarious Functions than the more specialized, and such 
animal tissues as are vicarious have conspicuously cellular 
composition. 
Something like a 'priori reasons may be reached for these 
a posteriori conclusions:—From evolution we know that life 
comes before organisation. Organic matter in a state of 
homogeneous aggregation precedes matter in a state of 
heterogeneous aggregation, and as passing from a structureless 
to a structured state is a vital process, it follows that vitality 
existed while yet there was no Structure. 
From the definition of life we know that inner actions 
become so adjusted as to balance outer actions, and as every 
advance in life is the better adjustment of inner to outer 
actions, and as increasing complexity of structure is only a 
means to that end, it follows that Function determines 
Structure; this is also true where modified Structure otherwise 
produced apparently initiates modified Function, for it is only 
where such so-called spontaneous modification of Structure 
subserves some advantageous action that it is permanently 
established. Heterogeneity of Structure and of Function are 
obviously connected. 
The progress of Structure and Function is parallel, for if 
Structure advances from the simple and general to the complex 
and special, so too must Function. 
EXPOSITION OF CHAPTER IV.-WASTE AND REPAIR. 
Waste and Repair are insignificant in the Vegetal 
Kingdom, either by consumption or reconstruction of tissue 
or by restoration of lost parts ; they are slight in lower 
animals, in reptiles, and even in fish, though active, but are 
great in active, hot-blooded animals, and such animals waste 
most when most in action, hybernating animals waste little, 
and in invalids waste diminishes as expenditure of force 
declines. 
The waste and repair of special parts is also in proportion 
to their activity, as is proved by common experience. 
“ Repair is everywhere and always making up for waste,” 
though the two processes vary in their relative rates, and 
reintegration is proportionate to disintegration, the organs 
continually taking up fresh materials from the blood enriched 
by food. 
The rapidity with which wasted organs recover, varies 
with the age and reparative power of the individual, and 
function carried to excess may never be made up. 
