374 TRANSMISSION 



this matter of constitutional vigor, which so largely depends 

 upon nutrition that the breeder can afford to make no mistake 

 at this point. 



Influences that strike at the root of the vital principle, what- 

 ever that may be, are far reaching in their consequences. To 

 maintain the vital powers at a maximum is one of the prime 

 objects in all breeding, and that this is to a large extent a 

 matter of nutrition is a fact that should be fully appreciated 

 by him who hopes to maintain unimpaired the valuable racial 

 characters for which he breeds his animals and his plants. 



There is no better maxim for the breeder than this : the 

 results of good feed are transmitted to the offspring in the form 

 of a vigorous constitution and large powers of assimilation and 

 of service. 



SECTION V EVIDENCE FROM ACCLIMATIZATION 



It is a well-known fact that the individual acquires by experi- 

 ence a high degree of resistance to temperature, poisons, or 

 other adverse conditions of life ; that this modification is more 

 or less permanent with the individual and that in good time the 

 race as a whole becomes acclimatized to changed but persistent 

 conditions. 1 Is this race acclimatization in any way the result 

 of transmission of the acclimatization of the individual ? 



1 It should be clearly understood that " acclimatization " is not confined to 

 adverse conditions ; it may relate as well to adaptation to improved conditions, 

 such as increased food supply. Indeed, the term is intended to cover accommo- 

 dation to any change in external conditions of life, whether favorable or unfavorable, 

 gradual or sudden. 



As is well known, acclimatization is more successful if the subjection be 

 gradual ; but, in any event, one of two results will follow if the individual is not 

 killed in the process: (i) it will become permanently altered, and will therefore 

 discharge its functions in a modified manner ; or (2) it will acquire by experience 

 so high a degree of resistance as to be able to resume its usual activities after 

 the first disturbance and afterward to discharge its normal functions in spite of 

 adverse conditions. 



There are thus two kinds of acclimatization : one in which the functions or 

 activities are modified, the other in which the individual succeeds in resisting the 

 changed conditions, and therefore in preserving its normal functions. Of the 

 two, the latter is perhaps the more common. The former betrays the more con- 

 stitutional change, the latter the greater elasticity in organization. 



