398 ON SENSATION, AND THE ORGANS OF THE SENSES. 



is doubtless to be in part attributed (as already remarked) to the increased 

 attention which is given to the sensations, and in part to an increased develop- 

 ment of the tactile organs themselves, resulting from the frequent use of them. 

 The case of Saunderson, who, although he lost his sight at two years old, be- 

 came Professor of Mathematics at Cambridge, is well known ; amongst his 

 most remarkable faculties, was that of distinguishing genuine medals from 

 imitations, which he could do more accurately than many connoisseurs in full 

 possession of their senses. The process of the acquirement of the power of 

 recognizing elevated characters by the touch, is a remarkable example of this 

 improveability. When a blind person first commences learning to read in this 

 manner, it is necessary to use a large type ; and every individual letter must 

 be felt for some time, before a distinct idea of its form is acquired. After a 

 short period of diligent application, the individual becomes able to recognize 

 the combinations of letters in words, without forming a separate idea of each 

 letter ; and can read line after line, by passing the finger over each, with con- 

 siderable rapidity. Now when this power is once thoroughly acquired, it is 

 found that the size of the type may be gradually diminished ; and this seems 

 to indicate, that the sensations themselves are rendered more acute, by the 

 frequent application of them in this direction. As an instance of the correct 

 notions which may be conveyed to the mind, of the forms and surfaces of a 

 great variety of objects, and of the sufficiency of these notions for accurate 

 comparison, the Author may mention the case of a blind friend of his own, 

 who has acquired a very complete knowledge of Conchology, both recent and 

 fossil ; and who is not only able to recognize every one of the numerous spe- 

 cimens in his own Cabinet, but to mention the nearest alliances of a Shell 

 previously unknown to him, when he has thoroughly examined it by his 

 touch. Many instances are on record, of the acquirement, by the blind, of 

 the power of distinguishing the colours of surfaces, which were similar in 

 other respects ; and, however wonderful this may seem, it is by no means 

 incredible. For it is to be remembered that the difference of colour depends 

 upon the position and arrangement of the particles composing the surface, 

 which render it capable of reflecting one ray whilst it absorbs all the rest ; and 

 it is quite consistent with what we know from other sources, to believe that 

 the sense of Touch may become so refined, as to communicate a perception 

 of such differences. 



526. The examples of peculiar acuteness of this sense, which we occa- 

 sionally meet witn among the lower animals, are very interesting, when 

 viewed in connection with its improveability in Man. It was found by Spal- 

 lanzani, that Bats, when deprived of sight, and (as far as possible) of hearing 

 and smelling also, still flew about with equal certainty and safety, avoiding 

 every obstacle, passing through passages only just large enough to admit them, 

 and flying about places previously unknown, with the most unerring accuracy, 

 and without coming into collision with the objects near which they passed. 

 He also stretched threads in various directions across the apartment, with the 

 same result. So astonished was he at these curious facts, that he was led to 

 attribute the phenomenon to the possession of a sixth sense, unknown to Man. 

 Cuvier was the first to appreciate the real value of these experiments, as afford- 

 ing a proof of the existence of the most exquisite tactile sensibility, over the whole 

 surface of the flying membrane ; the naked surface and delicate structure of 

 which, appear well adapted to constitute the seat of so important a function. 

 From this view, tberefore, it would appear that it is by means of the pulsation of 

 the wings on the air, that the propinquity of solid bodies is perceived, through 

 the manner in which the air reacts on their surface. It is curious that the 

 instance which (so far as we at present know) is most analogous to this, 

 should be met with among the inhabitants of the deep. It is a fact well 



