THE SENSE OF TASTE. 129 



tongue receives the peculiar impression which we call taste ; seemdly, whether, 

 besides the tongue, other parts of the cavity of the mouth are endowed with this 

 faculty ; thirdly, to what structural arrangements is it due I Strangely enough 

 the answers to the three questions are still in dispute, and in part at least are ex- 

 tremely defective. It would seem, on the whole, highly probable that to a very 

 small tract has been assigned the sense of taste, for with more exact exploration 

 its boundaries have been found to be more and more circumscribed. Wliile the 

 older physiologists acquiesced in the popular notion that the tongue is the organ 

 of taste, and ascribed to the whole mucous coat of the mouth, and even of the 

 jaws and pharynx, the faculty of exciting impressions of taste, most of the modern 

 school are unanimous in the opinion that only a small portion of the dorsum of 

 the tongue, and that indeed the hindmost and nearest to the throat, exercises the 

 prerogative of deciding on the sapid properties of transmitted substances. It is 

 true that there are those even now who regard the whole surface of the tongue, 

 including its under side, and even the mucous membranes which line the orifice of 

 the throat, as embraced within the province of this sense, but in our opinion im- 

 properly. No one, however, disputes that the hinder part of the dorsum of the 

 tongue is endowed with at least a finer sense of taste ; a conclusion which re- 

 ceives countenance from the commonly observed ftict that whenever it is proposed 

 to submit any substance to a closer scrutiny of the sense in question, we in- 

 stinctively transfer it to that portion of the mouth, where the hard palate also 

 lends its mechanical aid to the investigation ; while it never occurs to any one 

 to test the properties of taste with the point of the tongue, or to introduce the 

 object under the lower surface of that member. If it be difficult to prove con- 

 clusively that the rest of the mucous regions under review do not possess a sense 

 of taste, it certainly exists there in a much weaker and more obtuse degree. The 

 discrimination is not so easily made as might be supposed ; in such inquiries 

 there ore not a few incidental sources of error. In the first place, care must be 

 taken for trials of this sort, to choose substances which excite a pure and simple 

 sensation of taste, and not simultaneously a sensation of touch, which may readily 

 be confounded with the former. We ought not, for example, to select substances 

 having what is called a sharp, hot, or rough flavor, for those are qualities of a 

 sensation of touch, as are the pungent odors spoken of in our previous article on 

 the sense of smell. [See Smiths. Report for 1865.] Now, as the sense of touch 

 is unquestionably spread over the entire cavity of the mouth, it will be granted 

 that such substances as the above may readily lead to false conclusions respecting 

 the extent of the gustatory area. In the second place, it is of importance to the 

 proposed investigation that the substance submitted to proof should not be con- 

 veyed through the medivim of the saliva, in which it is of course dissolved, (for 

 only soluble substances are capable of being tasted,) to other regions of the oral 

 cavity, and so be carried to that hinder part of the tongue, whose especial sus- 

 ceptibility to such impressions is admitted. Nor, for this, is any movement of 

 the saliva necessary ; as a lump of sugar placed at the bottom of a vessel of 

 water will, in dissolving, gradually diffuse itself through the whole mass and 

 reach the surface, so may the solution of a similar substance introduced beneath 

 the tongue penetrate the salivary stratum which overlies every part of the cavity, 

 and attain the nerves of taste situated elsewhere. If this be the case, it will of 

 course be difficult to determine the exact seat of the sensation. On the other 

 hand, we are always prone to refer the sensation of taste to the point to which, 

 by virtue of the sense of place, (Ortssinn,) we refer the impression of touch pro- 

 duced by the contact of the substance with the ends of the nerves of feeling In 

 what way this perception of place which connects itself with the sensation of 

 touch arises, has been discussed at large in our previous essay on the sense of 

 feeling. [Smithsonian Report, 1865.] 



If the proposed inquiry be conducted with scrupulous regard to the precau- 

 tions indicated, the conclusion, we think, can scarcely fail to be reached that 

 9sC6 



