386 THE POPULAR SCIENCE MONTHLY. 



ticularly in domesticated animals, because inlierent organic con- 

 servatism carries into the new state of life habits and instincts 

 useful to the old. The turning round of a dog before it goes to 

 sleep, and what my children call the " kneading-dough " action of 

 a cat when before a warm fire, have been noticed before. But it 

 may be remarked that when a cat takes a piece of meat she inva- 

 riably gives it a shake a habit acquired by the wild animal to 

 shake off blood-drops and any adherent grit obtained by the flesh 

 from contact with the ground, but an entirely useless performance 

 in the case of a domestic cat fed on cooked meat in a carpeted 

 room. Ducks which are kept away from a pond will, when it 

 rains, or when they hear the splashing of water, repeatedly raise 

 and lower their heads with a jerking motion the same action 

 which they use when in the water in order to throw the water 

 over their bodies to wash themselves. Ducks delight in water, 

 and consequently these washing movements are intimately asso- 

 ciated with pleasure. Thus they feel pleasure when they are let 

 out after confinement, though they may not be near water ; and 

 this pleasure they express by going through the washing move- 

 ments in fact, the association is so strong that these movements 

 have become a conventional expression of pleasure of any kind. 

 Young lambs will mount any hillock in a field, because their wild 

 parents were dwellers in mountainous countries. We ourselves, 

 when we wish to express scorn, or contempt, or anger, draw up 

 our lip so as to expose the canine teeth the weapons with which 

 our monkey ancestors were wont to fight, as has frequently been 

 pointed out. Babies, when they cry and thus wish to express' 

 rage and indignation draw the mouth into a quadrate shape. 

 This peculiar set of the mouth in a crying infant was noted by 

 Darwin ; * but the reason for it does not seem to have been 

 grasped. It arises, however, from the fact that crying is asso- 

 ciated with anger, that in anger the fighting instinct is dominant, 

 that the fighting instinct leads to a display of weapons on the 

 noli- me-tang ere principle, that the weapons of our ancestors were 

 caniniform teeth in the upper and under jaws. It may be ob- 

 served that the lips of a crying baby's mouth are so disposed as 

 to exactly display the caniniform teeth as much as possible ; but 

 here comes the curious part of the whole matter a young baby 

 shows the quadrate-shaped mouth more remarkably than older 

 children ; yet it has no teeth to display, for the teeth are not to 

 be seen in the gums. Here is a habit, acquired for a definite pur- 

 pose, persisted in afterward when no means are available for ful- 

 filling the purpose, and yet persisted in because of the long asso- 

 ciation in ancestors of the weapon-display with anger. For a 



* Expression of the Emotions, second edition, chapter vi, pp. 155-158. 



