GROWTH. 131 



the above-named contrast between the ox and the sheep. A 

 calf and a lamb commence their physiological transactions on 

 widely different scales ; their first increments of growth arc 

 similarly contrasted in their amounts ; and the two diminish- 

 ing series of such increments, end at similarly-contrasted 

 limits. 



$ 49. Such are the several conditions by which the phe- 

 nomena of growth are governed. Conspiring and conflicting 

 in endless different ways and degrees, they in every case 

 qualify more or less differently each other's effects. Hence 

 it happens that we are obliged to state each generalization as 

 true on the average, or to make the proviso — other things 

 equal. 



Understood, in this qualified form, our conclusions are 

 these. First, that growth being an integration with, the 

 organism, of such environing matters as are of like nature 

 with the matters composing the organism, its growth is de- 

 pendent on the available supply of such matters : this is alike 

 a truth established by experience, and an inference from the 

 truth given in our forms of thought {First Principles, § 67). 

 Second, that the available supply of assimilable matter being 

 the same, and other conditions not dissimilar, the degree of 

 growth varies according to the surplus of nutrition over ex- 

 penditure — a generalization which is illustrated in some of 

 the broader contrasts between different divisions of organ- 

 isms, and is a direct corollary from the persistence of force. 

 Third, that in the same organism, the surplus of nutrition 

 over expenditure is a variable quantity ; and that growth is 

 unlimited or has a definite limit, according as the surplus 

 does or does not progressively decrease. This proposition we 

 found on the one hand exemplified by the unceasing growth 

 of organisms that do not expend force ; by the growth, slowly- 

 diminishing but never completely ceasing, of organisms that 

 expend comparatively little force ; and by the definitely 

 limited growth of organisms that expend much force ; and 



