482 HOMOLOGY OF PALATINE PROCESS, 



In man a somewhat similar condition exists, though he differs 

 from Pteropus in having a rudimentary organ of Jacobson. Here 

 there is no palatine process to the premaxillary, and the rudi- 

 mentary recurrent cartilage — ^the plough-share cartilage of Huscke 

 — is not supported by a distinct bone; but in a human foetus of 

 10 weeks I have found on the inner side a small tract of osteo- 

 genetic cells very similar in position to those in Trichos7j.ru s, but 

 here ossified by an invasion from the vomer. 



In Ornithorhyvchus we find still further evidence of the 

 vomerine nature of the bony support of Jacobson's cartilage. 

 Here in the adult we find the capsule of Jacobson's organ 

 supported by the median " dumbbell -shaped bone " — a structure 

 which bears a very marked resemblance to the little median bone 

 lying between the organs in the ])at. Since its first discovery 

 this peculiar dumbbell-shaped bone has been the subject of very 

 considerable discussion as to its true nature. Three different 

 opinions have been expressed with regard to it, but as one of 

 them — that homologising it with the prenasal bone of the pig — 

 has been abandoned by its author, and is known to be founded 

 on a misconception, only the other two need be discussed. The 

 view which has received almost universal support — that of 

 Rudolphi, Meckel and Owen — is that it is the inner part of the 

 premaxillary and the homo/o;/ue of the palatine process of the 

 premaxillary in the higher mammals. In more recent times 

 Albrecht,* Turner,! Flower t and Symington^ have advocated the 

 same view, and have adduced arguments which practicall}^ amount 

 to conclusive proof of the correctness of their position. The other 

 view which has been expressed as to its nature is that recentlj^ 



* Loc. cit. 



t \V. Turner, " The Dumbbell-sliaped Bone in tlie palate of the Ornitho- 

 rhynchus compared with the Prenasal Bone in the Pig." Journ. Anat. and 

 Phys. Vol. xix. 



X W. H. Flower, " Osteology of the Mammalia." .Srd Ed. Lond. 1885. 



§ J. Symington, "The Nose, the Orgun of Jacob.son, and the dumbbell- 

 shaped bone in Ornithorhynchus." Proc. Zool. Soc. 1891. 



