EVOLUTION AND ITS CONSEQUENCES. 19 



If, as I suppose, these additions, either adaptive or non-adapt- 

 ive, be produced by an acceleration * of growth, it is evident that 

 the same immediate cause of that increase must be potent in both 

 cases. That one of the *^ forces" is concerned in growth as well 

 as in all the active animal and vegetable processes, is obvious to 

 those who have carefully observed it. The fact that growth, like 

 work, requires food for its progress and continuance, is reason 

 enough for suspecting the existence of a force, and in some cases 

 the relation between this force and other known forces may be 

 measured. 



Prof. Henry pointed out these facts many years ago, and 

 illustrated them by observations on the growth of the potato and 

 of the Qgg. The starch of the former, a complex ''organic" 

 chemical compound, weighs much more than the young shoot 

 of cellulose, etc., into which it is converted by the process of 

 growth, so that a portion of the substance of the tuber has evi- 

 dently escaped in some other direction. This was found to be 

 carbonic-acid gas and water, derived from the slow combustion of 

 the starch, which, in thus ''running down " from the complex or- 

 ganic state, to the more simple inorganic compounds, evolves an 

 amount of force precisely equal in amount to the chemical force 

 (chemism) requisite to bind together the elements in the new and 

 complex substance cellulose, f 



It is well known that substances differ in their capacities for 

 giving out different kinds of force. This, of course, means their 

 capacity for converting one kind of force into another. Thus, if 

 glass be rubbed with silk, the motion is converted into electricity, 

 "while, if it be rubbed by the hand, heat is the principal result. 

 In some cases chemical force, set free by decomposition, is con- 

 verted into light ; in others, heat ; in others, to electricity, often- 

 er to several at once. But one substance, so far as known, pos- 

 sesses the power of converting this chemical force or heat into 

 growth-activity, and that is the material out of which the living 

 parts of animals and plants are composed. This is a protein, a 

 compound of carbon, oxygen, and nitrogen in the order of rela- 

 tive quantity, with a smaller proportion of hydrogen, the whole 

 being often associated with still smaller quantities of sulphur 



* For the definition of this term see first article, in May number of '* Penn 

 Monthly." (Antea, p. 11.) 



f "Agricultural Report of Patent Office," 185*7. 



