CHAPTER XXXV. 



THE OLFACTORY ORGAN. 

 BY PROFESSOR BABUCHIN. 



THREE parts must be distinguished in the organ of smell, (a) 

 The apparatus for receiving the impressions of odours ; (6) the 

 conducting apparatus ; and (c) the central organ to which the 

 odorous impressions are carried by the conducting apparatus. 



The first, and a part also of the second apparatus are imbed- 

 ded in the mucous membrane which, amongst the higher ani- 

 mals, covers the uppermost and the deepest parts of the nasal 

 cavities ; whilst in some of the lower Vertebrata (naked Am- 

 phibia) it extends as a kind of elevation on this or that wall 

 of the simple nasal passage ; and in others, as in Fishes, forms 

 manifold but regularly arranged folds rising from the floor of 

 the olfactory furrows, between or on which the odour-perceiving 

 elements occur. It is impossible to give here an elaborate de- 

 scription of all the peculiarities of the external modifications of 

 the olfactory organ in all animals ; this rather belongs to the 

 domain of comparative anatomy. Our duty is to furnish an 

 account of the physiologically active elements of this organ, 

 and their different relations to one another. 



The mucous membrane which contains the odour-perceiving 

 elements, presents certain peculiarities, by means of which it 

 can be distinguished, even with the naked eye, from the rest of 

 the nervous mucous membrane. It either possesses a yellow- 

 ish colour, as in Man, the Sheep and Calf, or is of a brownish 

 tint, as in the Guinea-pig, Rabbit, Dog, and other Mammals. 

 On this account the term locus luteus has been applied to it. 

 But inasmuch as this spot is not characterized in all animals 

 by a peculiar colour, another name, the regie olfactoria, is per- 

 haps preferable, which, however, only indicates that part of 



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