90 BIOLOGICAL SOCIETY OP WASHINGTON. 



size, it now involuntarily accompanies the somewhat changed emo- 

 tion of which some of the phases are extinct. It is not very rare to 

 find persons who can make the hair over the fi^ont of the head 

 bristle at will. Rage is habitually expressed by uncovering the 

 teeth, which is, in the lower animals, an attempt to frighten their 

 enemies by a show of weapons. This expression may become soft- 

 ened and modified to express the milder emotions of contempt and 

 disdain. I have met a lady who has to perfection the rather rare 

 accomplishment mentioned by Darwin of drawing up the upper lip 

 in a triangular notch directly over the canine teeth so as to display 

 them alone, usually on one side at a time. This most expressive 

 gesture of disdain can be performed under the influence of the 

 emotion by many who cannot do it at will. 



Of an opposite class are certain higher expressions, which, having 

 arisen later, are not yet entirely fixed. Blushing is one of the 

 most curious of these. It is not found in infants, and varies greatly 

 in frequency and amount in adults, accompanying the sentiment of 

 modesty, almost unknown among animals. The reddening is 

 usually confined to the face and neck. Darwin suggests an in- 

 genious explanation for this. The blood-vessels most exposed to 

 variations of temperature acquire the habit of expanding and con- 

 tracting — their vaso-motor nerves become more sensitive. The 

 chief expression of personal appearance is in the face ; the attention 

 of the mind is, therefore, directed there whenever the emotion of 

 modesty is aroused. This interferes with the ordinary tonic con- 

 traction of the blood-vessels, and an excess of blood suffuses the 

 surface. 



A remarkable confirmation of Darwin's views is the recent discov- 

 ery of localized centers in the brain which control emotional ex- 

 pression, and exist in animals as well as in man. It may some- 

 time be possible to read the currents and counter-currents of the 

 brain by means of feature-play with a precision approaching that 

 by which we estimate the force of a distant battery by the play of 

 a galvanometer needle. Many phenomena of expression, which 



