Page:Popular Science Monthly Volume 17.djvu/648

630 of one or two days, especially in relation to temperature. The earliest sensations of temperature are, however, of less immediate psychogenetic significance than those of touch. The hands of the child are the feelers of his soul. Through the excitation of the tactual corpuscles, at the points of the fingers and in the lips, the infant receives the first knowledge of things without him; and through the difference in the sensations arising from the touch of his own skin and that of foreign objects is the foundation laid for self-consciousness on one side and for making experiments on the other. His fingers are, in fact, the instruments with which he endeavors to explore everything that comes within his reach.

Professor Kussmaul has described some important experiments on the sense of taste in infants, in which he found that all new-born children could distinguish strong tastes, and that a very different reaction took place when the tongue was wet with a solution of sugar, from that which followed the application of quinine, vinegar, or salt. Signs of distaste were excited by the three latter substances, and of satisfaction by the sugar, which showed beyond doubt that the power to discriminate tastes begins at birth. The opinion that infants will take alike whatever is offered them holds good if at all, only of substances whose taste is weak. If the child seems displeased at the taste of a strong solution of sugar, as sometimes happens, that is only the effect of the surprise which all new intense sensations occasion. After the first trial, it will want more sugar, and show its satisfaction at getting it. The same is the case with the young of animals, which readily distinguish tastes and seem astonished at new ones; and the newly hatched chicken will at once select the food, where it is given a choice, which is most agreeable to it. Taste is, then, the first sense which affords clear perceptions, and is the first which gives occasion for the exercise of the faculties of memory and judgment.

The sensations of smell can hardly be separated from those of taste. Infants appear able to distinguish odors very early, but to what extent has not been ascertained. They are able to tell one kind of food from another by this means, and have been known to decline the acquaintance of a new nurse whose presence was disagreeable to them. It is known that animals that are born blind are guided to their food—the mother's milk—by this sense. Some odors, as that of tobacco smoke, have been found to be disagreeable to young animals; others, as that of camphor, pleasant.

All infants are deaf at birth, because the outer ear is as yet closed, and there is no air in the middle ear. A response to a strong sound is observed, at the earliest, in six hours, often not for a day, sometimes not for two or three days. The awakening of the sense may be recognized by means of the drawing up of the arms and the whole body, and the rapid blinking which a loud noise provokes; and it is a sign of deafness if the child, after its ears have had time to come into a