Chap. XIV. AND SUMMARY. 363 



not worth looking at, would not probably have been ac- 

 quired until a much later period. 



Of all expressions, blushing seems to be the most 

 strictly human; yet it is common to all or nearly all the 

 races of man, whether or not any change of colour is 

 visible in their skin. The relaxation of the small arteries 

 of the surface, on which blushing depends, seems to 

 have primarily resulted from earnest attention directed 

 to the appearance of our own persons, especially of our 

 faces, aided by habit, inheritance, and the ready flow 

 of nerve-force along accustomed channels; and after- 

 wards to have been extended by the power of associa- 

 tion to self-attention directed to moral conduct. It can 

 hardly be doubted that many animals are capable of 

 appreciating beautiful colours and even forms, as is 

 shown by the pains which the individuals of one sex take 

 in displaying their beauty before those of the opposite 

 sex. But it does not seem possible that any animal, until 

 its mental powers had been developed to an equal or 

 nearly equal degree with those of man, would have 

 closely considered and been sensitive about its own per- 

 sonal appearance. Therefore we may conclude that 

 blushing originated at a very late period in the long line 

 of our descent. 



From the various facts just alluded to, and given in 

 the course of this volume, it follows that, if the structure 

 of our organs of respiration and circulation had differed 

 in only a slight degree from the state in which they now 

 exist, most of our expressions would have been wonder- 

 fully different. A very slight change in the course of 

 the arteries and veins which run to the head, would prob- 

 ably have prevented the blood from accumulating in 

 our eyeballs during violent expiration; for this occurs 

 in extremely few quadrupeds. In this case we should 

 not have displayed some of our most characteristic ex- 



