134 ON THE SENSES. 



is supplied by the enveloping projections of the mucous membrane which enter 

 into corresponding cavities of the epithelium. We are aware that this, teleo- 

 logical mode of considering anatomical arrangements as directed to a pre-deter- 

 mined end, and contrived with a view to attaining that end, will at present be 

 received in. many quarters with entire repugnance; wherefore we shall not here 

 further insist upon it. Enough, if the preceding example should serve to show 

 how well this manner of viewing the subject is adapted to lead us to an under- 

 standing of such arrangements. The clearest method of explaining natural as 

 well as artificial mechanism is, in our opinion, that which bases itself upon teleo- 

 logical principles ; how far the employment of teleology for purposes of demon- 

 stration may be justified is another question 



Returning to a consideration of the papillae we remark that, for. a proper con- 

 ception of them, attention should be especially directed to the delicate structure 

 of the small secondary projections of the mucous membrane, with a view to 

 seeking therein the ends of the nerves and apparatus of sensation. But hitherto 

 all efforts have been fruitless, nor has research in this direction been rewarded 

 with the slightest degree of certainty. Neither in the filiform, nor fungifoim, 

 nor circumvallate papillse has success attended the attempt to explore the ulti- 

 mate destination of the nerves which direct their minute filaments with extreme 

 intricacy towards the surface, to follow them into the interior of the superficial 

 projections of the mucous membrane, and there detect a difference of arrange- 

 ments which might guide us to a decision respecting a difference of functions. 

 However probable the supposition that the filiform and fungiform papillff; con- 

 tain the ends and apparatus of the nerves of touch; that the circumvallate, on 

 the other hand, which occupy the centre of the seat of taste, and are outwardly 

 so strikingly distinguished, contain those of the nerves of taste ; yet we are 

 imable to furnish anatomical evidence for that supposition, or indeed to establish 

 it conclusively through physiological experiments. Even the peculiarity of ex- 

 ternal form of these latter papillae is a riddle ; we cannot explain what purpose 

 is subserved by their division into a roundish central elevation A, and an annular 

 periphery B, separated from one another by a distinct foss 0. If we ventured 

 to assert that this foss fui'nishes a sort of reservoir in which the solutions of 

 sapid objects are received in order, by longer contact with the sensitive surface, 

 to take more full effect on the extremities of the nerves, while the passage of 

 those solutions over a free surface might be too rapid for distinct perception, we 

 should only be advancing au empcy conjecture for which no proof could be alleged. 

 Nothing remains for us, therefore, but to wait until, by persevering and patient 

 observation, some deeper insight into the secret mechanism of the organs in ques- 

 tion shall be vouchsafed, and material be thereby furnished for physiological inter- 

 pretation. 



While it fares so unsatisfactorily with our knowledge of the organs of taste, we 

 are, unfortunately, not much better off as regards our knowledge of the nature and 

 conditions of the external influences which call forth a sensation of taste of what- 

 ever quality. We know well what substances produce such sensations, and bear 

 in mind a correct idea of the kind of impression connected with their use, so that 

 we again recognize the substances by that impression, or, even without their pres- 

 ence, easily recall, in imagination, the sour, or sweet, or bitter qualities which dis- 

 tinguish them. But this knowledge, in which the epicures must be recognized as 

 graduates, though the basis of our practical use of the sense of taste, avails us little 

 or nothing to a mastery of the physiological theory. We know even more : we 

 know accurately the physical and chemical properties of the greater number of 

 sapid substances, and are dumb notwithstanding to the capital question, what 

 property is it which makes a substance sapid, and qualifies it for the excitement of 

 such or such a sensation ? We know no single property common to all sapid mat- 

 ters which can be even remotely identified as the cause of their operation on the 

 nerves of taste, and in which we can seek the source of their peculiar action. To 



