Dr. Fleming, in his "Philosophy of Zoology," thus writes: "The sense of touch appears in man to be able to obtain nearly all the information, with regard to external objects, which it is capable of receiving. In a few instances, the lower animals surpass us in the delicacy of the sense, as the bat, which is warned indirectly by its aid of the presence of bodies previous to coming in contact with them. The feelers of insects are likewise better adapted for exploring the condition of the surface of bodies than any organ which we possess. But in all these the sensibility of touch is limited to particular qualities, or confined within narrow bounds. The human hand, on the contrary, by its motions, the pliability and strength of the fingers, and their softness, is the most extensive and perfect organ of touch possessed by any animal." The accuracy of the sense of touch is greatly improved by habit; and when its resources are in constant demand, as in the instance of persons deprived of sight, or born blind, its discriminating powers are wonderfully increased. The same observation applies also to the sense of hearing, which in blind persons generally is extremely acute and accurate in its perceptions. In a Monthly Volume, published by the Religious Tract Society, and entitled "Comparisons of Structure in Animals: the Hand and the Arm," the reader will find a general account of the structure and uses of the anterior limbs of man and the lower animals, and of the substitutes for the hand, as an organ of touch and prehension, with which many of the latter are provided. Dr. Fleming regards the "sense of heat" as distinct from that of touch, and, in fact, as claiming to be one of the senses. "The sense of touch," he writes, "is exclusively occupied with examinations of the conditions of resistance. Contact, therefore, is indispensably requisite for enabling the organ to act upon the object, and muscular exertion to examine its condition. Neither of these is necessary to enable the sense of heat to act. Caloric rays emanate from a heated body, though at a distance; and in order to ascertain their direction and intensity no muscular effort is required. When the heated body happens to be in contact with us, we in like manner examine its conditions in reference to temperature without any muscular exertions, or, rather, we try to avoid them. Thus, when I lay my hand upon the table to examine its hardness or smoothness, I make an obvious muscular effort with my fingers; but when I lay my hand upon the table to examine its temperature, I endeavour to check all motion, so as to keep my hand in the same position. These qualities of the sense of heat sufficiently distinguish it from that of touch, with which it has been confounded, and justify its establishment as a distinct power of perception."