ANIMAL PHYSIOLOGY. 



257 



ANIMAL PHYSIOLOGY. VIII. 



THE ORGAN OF 8MELL-(concIu < l*d). 



To us the sensations of nmoll are far less vivid and reliable than 

 those of sight and hearing, or even those of touch and taste. 

 This in shown by the fact, that the ideas which these sensations 

 leave behind them ore loss distinct : the memory retains them 



students in chemistry, will have been struck with the number of 

 men whose sense of smell is imperfect and unreliable ; and even 

 those who think they have this sense unimpaired are often misled, 

 from the fact that they are conscious of a sensation, not pro- 

 duced by odour, bat which is, in fact, only the general eense of 

 touch, common to the surface of the body, and only more 

 in the dfllioatfi lining membrane of thf nose. 





I. VERTICAL SECTION OF HEAD OF PORPOISE, SHOWING THE NASAL PASSAGE. II. VERTICAL SECTION OF BABBIT'S HEAD, SHOwnra Orrrm 

 WALL OF THE NASAL CANAL, LEFT SIDE. III. UNDER-SIDE OF HEAD OF SPOTTED DOO-FISH. IV. NASAL SAC OF STURGEON. 



Bef. to NOB. in Figs. I. 1, 2, cavities of the skull ; 3, septum between the lobes of the brain; 4, nasal passage ; 5, slit-ljjto orifice; 6, foblod 

 membrane ; 7, upper end of air-passage, grasped by the sides of the nasal canal ; 8, soft palate ; 9, hard palate ; 10, tongue ; 11, valve, 

 II. 1, cavity of the brain; 2, 3, ethmo-turbinals ; 4, lower turbinal; 5, nostril; 6, palate; 7, nasal canal; 8, bulls of ear; 9, bristle 

 running through Eustachian tube. 



for a shorter time, and will not reproduce them at will. More- 

 over, those sensations furnish but few starting-points for thought, 

 or speculation, or reason to proceed from. We seldom employ the 

 smell in investigation, unless it be upon objects which give no in- 

 dication whatever to any of the other senses ; and when wo do so, 

 wo are not satisfied until we have other confirmatory evidence 

 as to the nature of those objects. The chemist in the laboratory 

 will make use of this sense, as a rough-and-ready method of 

 detecting gases which cannot be otherwise easily dealt with, but 

 ho always confirms their presence by other tests if possible. 

 Any one who has presided over the practical experiments of 

 VOL. I. 



detect pungent gases like ammonia and chlorine, but cannot dis- 

 tinguish between them, or between aromatic gases like alcohol 

 and chloroform. On the whole, we make such little nee of oar 

 organ of smell, its acuteneea being as often an inconvenience M 

 an advantage to us, that we endure the loss of this sense with 

 more patience and with less sense of privation than that of any 

 other. The estimate we form from experience of the compara- 

 tively small value of this sense, is apt to make OB misjudge its 

 importance to the lower ^nimala. But if we imagine that the 

 impressions which this sense brings to animals are as dull, in- 

 distinct, and unreliable to their consciousness as to our*, a litu 



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