182 



an olfactory function, already hinted at by Jacobson, and which 

 KöLLiKEK tries to evade in a peculiar manner, are not to be got 

 out of the way. 



In this regard an observation of Herzfeld in connection with trie 

 venous sinus, with a strong circular layer of nonstriated muscular 

 fibres, which is found in the wall of the organ of the rat on the 

 inner side of the bony capsule, — cartilaginous in the majority of 

 the mammals — seems to me worthy of attention. He assumes that 

 the air will be sucked into the organ through contraction of the 

 sinus and the lessening of the volume of the wall, inside the rigid 

 capsule, caused b}^ this. 



If this appears to be the case in other animals also — the oppor- 

 tunity for research will probably present itself in a veterinary college — 

 then a sort of olfactory function would become comprehensible. It 

 would then also become clearer why the Cetacea and Pinnipedia 

 are nearly the only ') mammals in which the search for the organ ^) 

 of RuYSCH has been in vain. 



It is comprehensible that the Cetacea and Pinnipedia have lost 

 the true olfactory organ, adapted to aquatic life in earlier tishlike 

 ancestors, it became adapted to smelling in the air in later ancestors, 

 which lived on land as mammals. When these, in a still later 

 period, again went back to aquatic life, as Protocetacea and Proto- 

 pinnipedia, the true olfactory organ could not undergo this change 

 and became rudimentary or disappeared altogether. If the organ of 

 RuYscH in terrestrial mammals is always filled with liquid (mucus), 

 and does not need to adapt itself to smelling in the air, then there 

 is not the same reason for its disappearance in the Cetacea and 

 Pinnipedia as there is for the degeneration of the true olfactory 

 organ of the Cetacea. 



') One would expect the Sirenia here also. It is remarkable however thai Manalus, 

 according to Stannius (Lehrbuch 1846, p. 399) possesses an exceptionally well 

 developed Organon Vomeronasale. In some bats and catarrhine apes the organ has 

 disappeared through some cause or other, as in the Cetacea and Pinnipedia. 



2) The numerous morphological investigations on this organ have taught us 

 very little about its function. On histological grounds a sort of olfactory function 

 is not to be doubted, (c.f. amongst others M. von Lenhossek, Die Nervenurspriinge 

 und Endigungen in Jacobsonschen Organ des Kaninchens. Anat. Anzeiger. 1892). 

 This is about the only result, concerning the function which we can, after about 

 200 years, add to the words of the discoverer : "Inservire miicn excernendo existimo." 



