Thirst, Elimination Sources of Simpler Motives

Thirst

Drives to overt behavior arise also from dryness of the mucous lining of the mouth and throat. Usually this means also a certain amount of water deficiency in the tissues. Saliva usually keeps the mouth and throat moist. As the body tissues become dehydrated, the saliva is no longer secreted in quantity sufficient to supply moisture to the mouth and throat.

As thirst develops the child or adult becomes restless, and, in fact, shows about the same rhythm phases as in hunger: restlessness, satisfaction, and quiescence. The significance and strength of the drive resulting from this tissue need are similar also to those in the case of hunger. The mechanisms involved are ready to function at birth.

Elimination

Many diverse structures and functional processes are involved in the elimination of waste products from the body. Water is eliminated by the lungs, the kidneys, the skin, and the lower intestine. Carbon dioxide is eliminated by the lungs, soluble salts by the kidneys, salts in solution by the skin, and insoluble waste products by the lower intestine. Of psychological importance are the features of these processes which are subject to modification and control for desirable social development. Breathing and the elimination of waste products by the sweat glands of the skin are well established soon after birth and are little modified by child training except in so far as training in breathing is given for singing, sports, and the like. The eliminative functions involving the bladder and lower bowel are of significance in child training because of their bearing on social adjustments. Adequate control of these processes is necessary for the protection of society, that is, for reasons of sanitation. Their control has significance also because of the social taboos developed about them, such as shame and modesty.

Three phases are observed in the rhythms of bladder and lower bowel elimination, corresponding to those in hunger and thirst. First is the period of accumulating pressure which directly necessitates and stimulates elimination. It is followed by that in which some response is made satisfying the drive. Finally ensues the period of relaxation, rest, or quiescence so far as elimination is concerned. Apparently, sensory experiences are involved, both in the increasing pressure of distention and in the eliminative responses, because voluntary control otherwise would be impossible.

During the first few months of post-natal life these processes are involuntary, but with maturation comes the possibility of developing voluntary control. With increasing age the frequency of these two eliminative responses decreases. The eighth month is usually the time to begin training in voluntary bladder control, and by the age of two years the child normally will be able to keep himself dry in the daytime. Similar control while asleep is not developed so soon, but if training is begun shortly after the end of the first year, control may be expected normally to develop by the end of the third year. Training in voluntary bowel control usually may begin advantageously about the end of the first month, and regular habits may be expected to be established by the end of the third or fourth month. The value of shame as an incentive in developing adequate voluntary control is seriously questioned. Intestinal or digestive difficulties, of course, may be expected to interfere with the regular routine being established for these functions.