CHAPTER X 



RELATIVE STABILITY AND INSTABILITY OF LIVING MATTER 



In order to guide the student of breeding in forming his con- 

 ceptions as to what may and what may not be accomplished in 

 the way of modifying the form or function of domesticated ani- 

 mals and plants, everything is valuable which throws light upon 

 the degree of fixedness in living matter ; that is to say, in the 

 relations that happen to have become established between the 

 essential characters of existing species. 



When the student for a time bestows careful study upon varia- 

 tion and comes to realize how radical are some of the departures 

 from type and how sweeping are some of the deviations from the 

 normal, he is led to feel instinctively that living matter exists in 

 a state of extreme instability as regards both form and function, 

 and that almost anything is likely to happen. 



When, however, he considers that, through it all, distinct types 

 are preserved ; and when he notes the singular persistence of cer- 

 tain characters through all the vicissitudes of time and evolution, 

 reappearing generation after generation when they were supposed 

 to have been long lost, and in many cases lingering after their 

 usefulness is past and associated characters have been blotted 

 out, when he considers all this, the careful student will realize 

 that stability and instability are relative terms, and he will begin 

 seriously to inquire into the degree of stability of the various plans 

 upon which matter has been organized and vitalized. It is there- 

 fore profitable to inquire somewhat fully into the relative stabil- 

 ity or instability of those compounds that are endowed with life, 

 and into their relative ability to maintain their integrity and dis- 

 charge their functions under conditions both normal and abnormal. 

 The utility of this inquiry rests in the light it may throw upon the 

 extent to which characters that have become typical are fixed and 

 unchangeable, and the extent to which they may be modified. 



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