CORRELATION OF VITAL AND PHYSICAL FORCES. 169 



physical or chemical conditions, such as light, nascency, etc., unite 

 and rise into plane No. 3, i. e., form organic matter. In both cases 

 there is chemical union under certain physical conditions ; but in the 

 latter there is one unique condition, viz., the previous existence then 

 and there of organic matter, under the guidance of which apparently 

 the transformation of matter takes place. In a word, organic matter 

 is necessary to produce organic matter ; there is here a law of like 

 producing like — there is an assimilation of matter. 



Again, physical force changes into other forms of physical force, 

 or into chemical force, under certain physical conditions ; so also 

 physical and chemical forces are changed into vital force under cer- 

 tain physical conditions. But, in addition, there is one altogether 

 unique condition of the latter change, viz., the previous existence then 

 and there of vital force. Here, again, like produces like — here, again, 

 there is assimilation of force. 



This law of like producing like — this law of assimilation of matter 

 and force — runs throughout all vital phenomena, runs to the minutest 

 details. It is a universal law of generation, and determines the ex- 

 istence of species ; it is the law of formation of organic matter and 

 organic force ; it determines all the varieties of organic matter which 

 we call tissues and organs, and all the varieties of organic force which 

 we call functions. The same nutrient pabulum, endowed with the 

 same properties and powers, carried to all parts of a complex organ- 

 ism by this wonderful law of like producing like, is changed into the 

 most various forms and endowed with the most various powers. There 

 are certainly limits and exceptions to this law, however ; otherwise dif- 

 ferentiation of tissues, organs, and functions, could not take place in 

 embryonic development ; but the limits and exceptions are themselves 

 subject to a law even more wonderful than the law of like producing 

 like itself, viz., the law of evolution. There is in all organic nature, 

 whether organic kingdom, organic individual, or organic tissues, a law 

 of variation, strongest in the early stages, limited very strictly by an- 

 other law — the law of inheritance, of like producing like. 



d. We have seen that all development takes place at the expense 

 of decay — all elevation of one thing, in one place, at the expense of 

 corresponding running down of something else in another place. 

 Force is only transferred and transformed. The plant draws its force 

 from the sun, and therefore what the plant gains the sun loses. Ani- 

 mals draw from plants, and therefore what the animal kingdom gains 

 the vegetable kingdom loses. Again, an egg, a seed, or a chrysalis, 

 developing to a higher condition, and yet taking nothing ab extra, 

 must lose weight. Some part must run down, in order that the re- 

 mainder should be raised to a higher condition. The amount of evo- 

 lution is measured by the loss of weight. By the law of conservation 

 of force, it is inconceivable that it should be otherwise. Evidently, 

 therefore, in the universe, evolution of one part must be at the ex- 



