additional appeal, good or bad; but all this simply illustrates the way instincts become modified, by combination with other instincts, and by the learning and fixing of various preparatory reactions that were not provided, ready-made, in the native constitution. The drinking instinct, or thirst impulse, is a very good example of this whole class of organic instincts. Instincts connected with hunger. Here again, the reactions nearest to the end-result (food in the stomach) are provided by nature. Sucking and swallowing appear at birth, chewing with the appearance of the teeth; and the infant also makes what seem to be instinctive movements of seeking the breast, as well as movements of rejecting it when satiated and of spitting out bad-tasting food. Putting food (and other things) into the mouth by the hands seems almost instinctive, and yet it has to be fixed by trial and error. Anything like definite food-seeking behavior, amounting to a _hunting_ instinct, scarcely gets a chance to show itself in {141} the human child, because his food is provided for him. In many animals, hunting is a highly organized instinct; thus, crouching, stalking, springing and teasing the mouse when caught, have been proved to be instinctive in young cats. Some animals have definite food-storing instincts also, and possibly food-storing shows the acquisitive or collecting tendency in its lowest terms. Possibly, that is to say, hunting and collecting, as well as disgust (primarily of bad-tasting or bad-smelling food), are originally parts of the food-getting behavior, having the general character of reactions preparatory to eating. However this may be, we can easily see the great importance of the hunger motive in human life; we have only to consider the matter in the same way as we considered thirst just above. Breathing and air-getting. Breathing, obviously a native reaction, is ordinarily automatic and needs no preparatory reactions, simply because air is so easy to get. But let breathing be difficult, for any reason, and the stifling sensation is as impulsive as hunger or thirst. The stuffy air in a cave or in a hole under a haymow will lead a child to frantic escape. Possibly the delight in being out of doors which shows itself in young children, and is not lost in adults, represents a sort of air-hunting instinct, parallel to food-hunting. Closely connected with breathing is the function of circulation, automatic for the most part; and we should mention also the organic needs of waste-elimination, which give impulsive sensations akin to hunger and thirst, and lead to more or less organized instinctive reactions. Responses to heat and cold.