298 ANATOMY. 



for scents to pass through it. This difficulty was endeavoured to be 

 obviated by imagining that they passed through the mucous membrane 

 of the mouth to that smelling membrane, in which case it might be 

 common to all insects, but which is not the case. For this explanation 

 of it appears to me forced, as well as a second advanced by Treviranus*, 

 who wishes to persuade us that the entire mucous membrane of the 

 mouth is the organ of smell, but then especially ascribes this sense to 

 haustellate insects. 



A different opinion is that formerly advanced by Baster, Dumeril, 

 and, latterly, by Straus Durkheim f, namely, that the margins of the 

 stigmata are smelling organs. We have, it is true, in favour of it, the 

 analogy of the organ of smell in the superior animals being seated at 

 the orifice of the respiratory organs, but that is absolutely all. The 

 mucous membrane, the nervous rete, and the nerves of smell, are all 

 wanting, or, at least, are not shown to exist. Perhaps, however, the 

 tracheae may possibly be organs of smell, if not at their aperture, yet 

 in their terminal ramifications, as they conduct air to all the organs, 

 and particularly likewise to the brain. Hence would follow the 

 deficiency of a peculiar organ of smell, which, however, must strike as 

 singular when we reflect upon the lower situated crab. But water 

 organs and organs of humidity, and such the organ of smell evidently 

 is J, for it is only with a moist nose that we can smell, more easily 

 attain a certain degree of perfection than in those which live in a rarer 

 medium. I will merely refer to the difference of the organs of smell 

 in water and land birds, as well as to the observation that the organs 

 of smell in birds are proportionably less perfect than in the amphibia 

 and fishes, which evidently helps to confirm the law, and serves to 

 explain the deficiency of these organs in insects. Thus insects, ac- 

 cording to my opinion, would smell with the internal superior surface, 

 if I may so call it, which is provided all over with ramifications and 

 nets of nerves, since this is always retained moist by the blood dis- 

 tributed through the body and by the transpired chyle, the same as is 

 surmised o the superior rnollusca, namely, the Pulmobranchia and 

 Cephalopoda, that their sense of smell is seated in their exterior inte- 

 gument and thus in a universally distributed smelling tunic. 



1 Vermischte Schriften. Vol. ii. p. 146. t Considerations, p. 421. 



The -whales want the auxiliary cavities of the nose, which secrete the fluid, because, 

 living in \vater, they do not require them. See Rudolphi Physiol. Vol. ii. PL I., p. 118. 



