On the Cartilago palatina and the Organ of Jacobson in sotne Mammals. 345 



half of the organ, that of the inner side being thicker than that 

 of the outer side. 



In the adult animal such a differenceMS hardly observable, 

 perhaps with the exception of the middle part. 



Having had no other adult specimen at my disposal than the 

 one examined before, I cannot add anything to what I have said 

 before on the highly rudimentary papillary cartilage found in that 

 individual, and I cannot therefore decide whether it is a structure 

 constantly occurring or not l . 



Neomys fodiens. 



I have examined one stage of Neomys fodiens, head-length 

 about 9 mm, consequently a rather old foetal specimen. Jndging 

 from tbis material, the organ of Jacobson in Neomys is essentially 

 similar to that in Sorex araneus. The arraogement of the cartilages 

 is about the same as in Sorex in front of the naso-palatine canals 

 and behind them, apart from the absence of the cartilago palatina. In 

 this stage at least, the outer part of the cartilago ductus naso-pala- 

 tini does not continue far behind the naso-palatine canals. 



The epithelium of the inner wall of the organ is thicker than 

 that of the outer wall, chiefly in the posterior half of the organ. 



As to the blood-vessels and the glands this stage does not 

 show anything remarkable. 



Crocidura russida. • 



With regard to the cartilaginous parts, as well as to the struc- 

 ture of the organ itself, the organ of Jacobson in Crocidura russida 

 differs from that of the above-mentioned shrews. 



The cartilages which form the floor of the nasal cavity are in 

 front of the naso-palatine canals connected with the base of the 

 nasal septum and laterally with the alinasal cartilages, forming a 

 continuous cartilaginous ring. Fig. 1 represents a section through 

 the cartilagines paraseptales (Jacobson's cartilages), the continuation 

 backwards of the nasal floor cartilage. As appears from the figure, 

 they have lost the connection with the nasal septum as well as with 

 the alinasal cartilages. 



1 A. Ärnbäck Christie-Linde, Der Bau der Soriciden und ihre Be- 

 ziehungen zu andern Sängetieren I. Morphol. Jahrbuch. Bd. XXXVI. 1907. 



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