276 DARWINISM STATED BY DARWIN HIMSELF. 



whole breadth of the forehead ; but, in the present case, 

 the middle fasciae alone are contracted. ; consequently, 

 transverse furrows are formed across the middle part alone 

 of the forehead. The skin over the exterior parts of both 

 eyebrows is at the same time drawn downward and 

 smoothed by the contraction of the outer portions of the 

 orbicular muscles. The eyebrows are likewise brought 

 together through the simultaneous contraction of the 

 corrugators ; and this latter action generates vertical fur- 

 rows, separating the exterior and lowered part of the skin 

 of the forehead from the central and raised part. The 

 union of these vertical furrows with the central and trans- 

 verse furrows produces a mark on the forehead which has 

 been compared to a horseshoe ; but the furrows more 

 strictly form three sides of a quadrangle. They are often 

 conspicuous on the foreheads of adult, or nearly adult, 

 persons, when their eyebrows are made oblique ; but with 

 young children, owing to their skin not easily wrinkling, 

 they are rarely seen, or mere traces of them can be de- 

 tected. 



VOLUNTARY POWER OVER THE GRIEF-MUSCLES. 



P <r 183 "^ ew P ersons > without some practice, can 



voluntarily act on their grief-muscles ; but, 

 after repeated trials, a considerable number succeed, while 

 others never can. The degree of obliquity in the eye- 

 brows, whether assumed voluntarily or unconsciously, dif- 

 fers much in different persons. With some who apparently 

 have unusually strong pyramidal muscles, the contraction 

 of the central fasciae of the frontal muscle, although it 

 may be energetic, as shown by the quadrangular furrows' 

 on the forehead, does not raise the inner ends of the eye- 

 brows, but only prevents their being so much lowered as 



