740 OF THE ORGANS OF THE SENSES, AND THEIR FUNCTIONS. 



other senses, that of Taste is capable of being rendered more acute by edu- 

 cation; and this on the principles already laid down in regard to Touch. 

 The experienced wine-taster can distinguish differences in age, purity, place 

 of growth, etc., between liquors that to ordinary judgments are alike; and 

 the epicure can give an exact determination of the spices that are combined 

 in a particular sauce, or of the manner in which the animal on whose flesh 

 be is feeding was killed. As in the case of other senses, moreover, impres- 

 sions made upon the sensory surface remain there for a certain period ; and 

 this period is for the most part longer than that which is required for the 

 departure of the impressions made upon the eye, the ear, or the organ of 

 smell. Every one knows how long the taste of some powerful substances 

 remains in the mouth ; and even of those which make less decided impres- 

 sions, the sensations remain to such a degree that it is difficult to compare 

 them at short intervals. Hence if a person be blindfolded, and be made to 

 taste substances of distinct, but not widely-different flavors (such as various 

 kinds of wine or spirituous liquors), one after another in rapid succession, he 

 soon loses the power of discriminating between them. In the same manner, 

 the difficulty of administering very disagreeable medicines may be sometimes 

 got over, by either previously giving a powerful aromatic, or by combining 

 the aromatic with the medicine; its strong impression in both cases prevent- 

 ing the unpleasant taste from exciting nausea. 



4. Sense of Smell. 



605. The Nasal passages may be considered as having, in air-breathing 

 Vertebrata, two distinct offices; for they constitute the portal of the Respira- 

 tory organs, and have for their office to take cognizance of the aeriform 

 matter as it enters them, and to give warning of that which would be in- 

 jurious (this being effected by the instrumentality of the Fifth pair), which 

 receives the impressions of gaseous irritants, and excites the act of sneezing 

 to expel them; whilst they also contain the organ of Smell, which is formed 

 by the distribution, over a certain part of their membranous wall, of the 

 0/factory nerve, which is susceptible of being impressed by Odorous emana- 

 tions. Of the nature of these emanations the Physical Philosopher is so 

 completely ignorant, that the Physiologist cannot be expected to give a 

 definite account of the mode in which they produce sensory impressions. 

 Although it may be surmised that they consist of particles of extreme 

 minuteness, dissolved as it were in the air, and although this idea seems to 

 derive confirmation from the fact that most odorous substances are volatile, 

 and vice versa, yet the most delicate experiments have failed to discover 

 any diminution in weight, in certain substances (as musk) that have been 

 impregnating a large quantity of air with their effluvia for several years; 

 whilst there are some volatile fluids, such as water, which to Man are entirely 



doxieal to say that wo are authorized to give greatest heed to the stomach, when it 

 Mimesis some seeming extravagance of diet. It may be said that this is a mere dep- 

 rivation of the sense of taste; but frequently it expresses an actual need of the stom- 

 ach, cither in aid of its own functions, or indirectly (under the mysterious law just 

 referred to) for the effecting of changes in the whole mass of blood. It is a good 

 practical rule in such cases to withhold assent, till we find after a certain lap^' <>t' 

 time that ihe same desire continues or strongly recurs; in which case it may gener- 

 ally be taken as the index of the fitness of the thing desired for the actual state of the 

 organs. J n the early stage of recovery from long gastric fevers, I recollect many 

 curious in>t inces of such contrariety to all rule being acquiesced in, with manifest 

 good to the patient. Dietetics must become a much more exact branch of knowledge, 

 before we can lie justified in opposing its maxims to the natural and repeated sugges- 

 tions of the stomach, in the state either of health or disease." 



