Animals which have hands appear to be the most acute; apes do things so resembling the mechanical actions of man that they seem to be actuated by the same sensations; but those animals which are deprived of hands having not any part divided and flexible enough to be able to twist round the superficies of bodies, they cannot have any precise notion either of the form or size of them. It is for this reason that we often see them frightened at objects which they ought to be the best acquainted with. The principal organ of their feeling is the muzzle, because it is divided in two parts by the mouth, and because the tongue serves them for touching bodies, and turning them, which they do over and over again, before they take them between their teeth. It may also be conjectured, that animals, which, as the scuttle-fish, the polypus, and many insects, have a great number of arms or paws, which they can unite and join, may also have an advantage over others, in knowing how to chuse what is most agreeable to them. Fishes, therefore, whose bodies are covered with scales, ought to be the most stupid of all animals, for they cannot have any knowledge of the form of bodies; and their sense of feeling must be very obtuse, since they cannot feel but through the scales. Thus all animals, whose bodies have no divided extremities, as arms, legs, paws, &c. will have much less sense of feeling than others. Serpents, however, are less stupid than fishes, because, although they have no extremities, and are covered with a hard and scaly coat, they have the faculty of bending round foreign bodies, and by that means obtaining some conception of their form and magnitude.
The two great obstacles to the exercise of the sense of feeling then are, first, the uniformity of the figure of the body of the animal, or the defect of the different divided and flexible parts; and secondly, the cloathing of the skin, whether with hair, feathers, scales, shells, &c. The more this cloathing is hard and solid, the less the sentiment of feeling will be; and the finer and more delicate the skin, the sense of feeling will be the more quick and exquisite. Women, among other advantages over men, have their skin more fine, and the sense of feeling more delicate.