GTIOWTH. 125 



seeming incongruities between it and certain facts inductively 

 established. Lest these should mislead him, it will be well 

 to explain them. Throughout the vegetal kingdom, 



he may remark that there is no limit of growth except what 

 death entails. Passing over a large proportion of plants 

 which never exceed a comparatively small size, because they 

 wholly or partially die down at the end of the year; and 

 pointing to trees that annually send forth new shoots, even 

 when their trunks are hollowed out by decay ; he may ask — 

 How does growth happen here to be unlimited ? The answer 

 is, that plants are only accumulators ; they are in no apprecia- 

 ble degree expenders. As they do not undergo a waste which 

 increases as the cubes of the dimensions, while assimilation 

 increases as their squares ; there is no reason why their 

 growth should be arrested by the equilibration of assimilation 

 and waste. Again, should he look among animals for an 



exact correspondence between the decreasing increments of 

 growth as ascertained by observation and as determined by de- 

 duction, he will not find it. And there are sufficient reasons 

 why the correspondence cannot be more than approximate. 

 Besides the fact above noted, that there are other varying 

 relations which complicate the chief one, he must bear in 

 mind that the bodies compared are not truly similar : the 

 proportions of trunk to limbs and trunk to head, vary con- 

 siderably. The comparison is still more seriously vitiated by 

 the inconstant ratio between the constituents of which the 

 body is composed. In the flesh of adult mammalia, water 

 forms from 68 to 71 per cent., organic substance from 24 to 

 28 per cent., and inorganic substance from 3 to 5 per cent.; 

 whereas in the foetal state, the water amounts to 87 per cent., 

 and the solid organic constituents to only 11 per cent. Clearly 

 this Ghange from a state in which the force- evolving matter 

 forms one tenth of the whole, to a state in which it forms two 

 and a half tenths, must greatly interfere with the parallelism 

 between the actual and the theoretical progression. Yet 



another difficulty may come under his notice. The crocodile 



