But in most cases habit, however prolonged, appears to have little effect on the constitution of the individual, and the fact has no doubt led to the opinion that acclimatization is impossible.
The subject of acclimatization is very little understood, and some writers have even denied that it can ever take place.
A consideration of these and many analogous facts might induce us to suppose that, among the higher animals at least, there is little constitutional adaptation to climate, and that in their case acclimatization is not required.
In the case of the latter class, however, acclimatization is a necessary preliminary to naturalization, and in many cases to useful domestication, and we have therefore to inquire whether it is possible.
There is indeed little or no evidence to show that any animal to which a new climate is at first prejudicial can be so acclimatized by habit that, after subjection to it for a few or many seasons, it may live as healthily and with as little care as in its native country; yet we may, on general principles, believe that under proper conditions such an acclimatization would take place.