For some days after they are brought into the world, most animals have their eye-lids closed. Infants open them the moment of their birth, but they are fixed and dull; they want that lustre which they afterwards acquire; and when they move, it is rather an accidental roll than an act of vision. The pupil of the eye is seen to dilate, or contract, in proportion to the quantity of light it receives, yet is incapable of distinguishing objects, because the organs of vision are still imperfect; the tunica cornea, or horny tunicle is wrinkled, and perhaps the retina is also too soft to receive the images of external objects, and admit the sense of seeing. The same remark is equally applicable to the other senses; they have not acquired that consistency which is necessary to their operations; and even when they have, a long time must elapse before the sensations of the infant can be just and complete. The senses are so many instruments which we must learn to employ. Of these sight, which seems to be the noblest and the most admirable, is also the most uncertain and delusive; and were its effects not every moment corrected by the testimony of touching we should constantly be misled and draw false conclusions. This sense of touching is the measure and criterion of all the others; it alone is essential to the animal's existence; and is alone diffused universally over its body. Yet, even this sense, in an infant just born, is imperfect; by its cries, indeed, it gives indication of pain; but it has no expression to denote pleasure. It is forty days before it begins to smile; about the same time also it begins to weep; its former expressions of pain being unaccompanied with tears. On the countenance of a new born infant there appears no vestige of the passions, the features of the face not having acquired that consistence and form which are necessary for expressing the sentiments of the soul. All the other parts of its body are alike feeble and delicate; its motions are unsteady and uncertain; it is unable to stand upright; its legs and thighs are still bent, from the habit it contracted in the womb; it has not strength enough to stretch forth its arms or to grasp any thing with its hands; and, if abandoned, it would remain on its back, without being able to turn itself.