PLUMAGE IN HEN-BIRDS. 198 



partridges are not so visible as in summer. The 

 same observation may apply to other birds. 



Upon the whole, therefore, I am disposed to 

 conclude, that this change of plumage in old hens, 

 is not alone confined to one, two, nor three dif- 

 ferent species, but that probably the same dispo- 

 sition is common to numbers of the feathered race, 

 the variations and changes of whose plumage, as 

 influenced by age, climate, food, confinement, or 

 disease, have not yet occupied a sufficient share of 

 attention ; and that the change is almost always 

 natural, produced either by the effects of age, of 

 sterility, or other causes, which tend to work some 

 changes in the constitution of birds. 



I am disposed to allow with Mr Hunter, that 

 something similar takes place in the human species ; 

 for that increase of hair, observable in the faces of 

 many women advanced in life, is certainly an ap- 

 proximation towards a beard, which is one of the 

 most distinguishing secondary properties of men. — 

 To this observation I may likewise add another, 

 viz. That mares, when old, approach the form of 

 the entire horse, by rising more fully at their necks. 



Without seeking to multiply these observations, 

 by going farther into the animal creation, I think 

 that I have advanced enough to warrant the follow- 

 ing conclusions. 



1st, That in order to separate and distinguish the 

 sexes, Nature has affixed certain external characters 

 proper to each. 



vol. in. n 



