EXPRESSION. 63 



prominence to. It occurs also in attempts to see 

 distinctly external objects, helping to shade from 

 dazzling surroundings, and concentrates the at- 

 tention on a limited field ; and, in exercising the 

 internal perceptions when a difficulty is encoun- 

 tered, the forehead falls into the same condition 

 as when a difficulty in distinguishing an object 

 with the eye is met with. These explanations 

 appear to me more satisfactory than to sup- 

 pose that the frown is the relic of childhood's 

 screaming, 1 the more so as in the worst cases of 

 screaming in childhood the eyes are not protected 

 by a frown at all, but by the violent closure of the 

 lids by means of the orbicularis, so that the infantile 

 frown is rather derived from the same source as the 

 frown of the adult than the parent of it. 



The formation of " rectangular furrows " on the 

 forehead, with elevation of the inner part of the 

 eyebrow, is more complex, and demands reference 

 to the anatomy of the muscles. Undoubtedly we 

 owe to Duchenne the knowledge, which anatomists 

 ought to have perceived before, but did not, that the 

 pyramidalis nasi is antagonistic to the central fibres 

 of \hzfrontalis. It is attached to bone below, while 

 the more fixed attachment of fazfrontalis muscle is 

 above. For a much longer time we have known the 



1 Darwin, op. cit. p. 225. 



