712 THE POPULAR SCIENCE MONTHLY. 



which, though very diverse, present no definite combinations. Its 

 composition, no doubt, is definite, and equally so its properties ; but 

 they are variable, and its variations alter the relations of the environ- 

 ment to the living being. To all changes of the environment there 

 are corresponding changes in the living being, otherwise it would 

 perish. These changes, which follow the laws of vital changes, inas- 

 much as they are in a definite combination, constitute the activity of 

 the animal ; the more numerous and frequent they are, the more active 

 is the life and the higher the rank of the living being in the scale of 

 life. The degree of correspondence between the living thing and its 

 environment is also its degree of life, inasmuch as in efl^ect it connotes 

 an increase in the number and iu the mutual dependence of the vital 

 changes which constitute life. A perfect correspondence would imply 

 a perfect life. If to all changes of the environment there were op- 

 posed, as a counterbalance, changes in the living thing, natural death 

 would be no more, nor death by disease or by accident, all of which 

 are signs of a lack of correspondence.' 



A definition of life which possesses these characters, and which 

 expresses in a general formula the law of the changes of structure, 

 and of the changes of function accompanying them ; that is to say, 

 which expresses the heterogeneity, the coordination, and the ever-in- 

 creasing mutual dependence of these changes ; and which at the same 

 time expresses the ever-increasing correspondence which attaches 

 them to the changes of the environment by an operation of equilibra- 

 tion such a definition makes life to be an evolution, a succession of 

 states of unstable equilibrium tending to perfect equilibrium ; not 



' We must here point out an erroneous statement made by Claude Bernard. In 

 his article on the "Definition of Life" {Revue des Deux Mondes, 15 Mai, ISTS, p. 345), 

 this eminent physiologist offers as a complete definition of life a portion of Spencer's 

 definition, as found in the " Principles of Biology." " The following definition," 

 says he, " is proposed by Herbert Spencer : ' Life is the definite combination of het- 

 erogeneous changes, both simultaneous and successive.' " And he goes on to say : 

 " Under this abstract form the English philosopher would specially indicate the idea of 

 evolution and of succession observed in vital phenomena." KM. Claude Bernard had made 

 this quotation from the "Principles of Biology" itself, he would have read immediately 

 after this passage the following words: "This is a formula which fails to call up an ade- 

 quate conception. And it fails from omitting the most distinctive peculiarity the 

 peculiarity of which we have the most familiar experience, and with which our notion of 

 life is, more than with any other, associated. It remains now to supplement the definition 

 by the addition of this peculiarity" (p. 71). Those who have studied Mr. Spencer's 

 writings know how cautiously he sets about making a definition. He completes a formula, 

 first expressed in very general terms, by the successive addition of essential characters, 

 and for each of these characters he makes a minute analysis. Thus, having given as a 

 preliminary result the formula quoted by M. Claude Bernard, Mr. Spencer adds that it needs 

 to be completed, and a few pages further on (p. 74) he adds these words : " In corre- 

 spondence with external coexistences and sequences." Again (p. 80), he writes : " The 

 broadest and most complete definition of life will be The continuous adjustment of 

 internal relations to external relations." It is evident that M. Claude Bernard did not 

 derive from the " Principles of Biology " the definition he quotes, and which he con- 

 demns. But ought he not to have taken it from that work '? 



