newly born baby to retract the corners of the lips in order to expose teeth which are still hidden in the gum is a ludicrously futile process; yet it shows in an extraordinary manner that a habit once acquired may remain, polarized, as it might be called, long after all reason for its acquirement and use had passed away.
From sadness to joy is a very welcome transition; and consequently a few remarks upon the method of expressing pleasure will not unsuitably follow those on the expression of pain. To show that they are pleased, human beings frequently draw up and wrinkle the nose the while they elevate the upper lip so as ta expose the teeth. The same action may be noticed in terriers to express pleasure, and it is called "grinning": in children it is a remarkably common feature. It is not general among adults; but when it be a regular habit in any individual it leads to the formation of obliquely transverse furrows each side of the nose, and so gives to the face a definite and somewhat amiable expression, which may degenerate into an unfortunate peculiarity.
The origin of this expression does not seem to have been any wish to expose the teeth, but rather a desire to sniff in as much as possible. Animals derive their greatest pleasures from the satisfaction of the sexual and gastric appetites; and all odors associated with such satisfaction would become pleasing, because they would suggest pleasant ideas to the senses. It would be pleasant, then, to inhale such odors, as the odor of a good dinner is pleasant to a hungry man about to enjoy it; and he expresses his satisfaction by sniffs. The rapid repetition of a series of sniffs in succession, necessitating certain convulsive movements of the stomach, may have been the initiation of that expression of delight called "laughter," which consists in a series of quick convulsive stomachic movements coupled with certain guttural cacklings.
What might be called the genesis of our expressions, or their historical development in the phyletic series to which man belongs, opens a very wide field. Darwin has attacked it in his Expression of the Emotions; but, though he has collected a great store of most interesting facts, the theories and conclusions which he formed in connection therewith are sometimes not so satisfactory as they should be. Particularly does this apply to his principle of antithesis, which it is admitted in a note to the second edition (page 52) has not met with much acceptance. This can hardly be wondered at; because it seems so totally opposed to that gradual acquirement and development which the Darwinian doctrine supposes. Space does not allow a further consideration of this subject, more than to say that, like other animals, children's actions when at play show mimic warfare and perverted inheritance of sexual instinct. Love and war, which played such important parts among prehuman ancestors, have left their mark