APPENDIX A. 



THE GENERAL LAW OF ANIMAL FERTILITY. 



[In the Westminster Review for April, 1852, I published an 

 essay under the title " A Theory of Population deduced from the 

 General Law of Animal Fertility,'''' That essay was the germ of 

 Part VI of this work, " The Laws of Multiplication,'''' in which its 

 essential theses are fully developed. When developing them, I 

 omitted some portions of the original essay — one which was not di- 

 rectly relevant, and another which contained a speculation open to 

 criticism. As indicated in § 74/, I find that this speculation has 

 an unexpected congruity with recent results of inquiry. I therefore 

 decide to reproduce it here along with the definition of Life pro- 

 pounded in that essay, which, though subsequently replaced by the 



definition elaborated in Part I, contains an element of truth.^ 

 ***** 



Some clear idea of tlie nature of Life itself, must, indeed, form 

 a needful preliminary. We may be sure that a search for the 

 influences determining the maintenance and multiplication of 

 living organisms, cannot be successfully carried out unless we 

 understand what is the peculiar property of a living organism — 

 what is the widest generalization of the phenomena that indicate 

 life. By way of preparation, therefore, for the Theory of Popu- 

 lation presently to be developed, we propose devoting a brief 



space to this prior question. 



***** 



Employing the term, then, in its usual sense, as applicable only 

 to organisms. Life may be defined as — the co-ordination of actions. 

 The growth of a crystal, which is the highest inorganic process 

 we are acquainted with, involves but one action — that of accre- 

 tion. The growth of a cell, which is the lowest organic process, 

 involves two actions — accretion and disintegration — repair and 

 waste — assimilation and oxidation. Wholly deprive a cell of 

 oxygen, and it becomes inert — ceases to manifest vital phe- 

 nomena ; or, as we say, dies. Give it no matter to assimilate, 

 and it wastes away and disappears, from continual oxidation. 

 Evidently, then, it is in the balance of these two actions that the 

 life consists. It is not in the assimilation alone ; for the crystal 



577 



