THE ORGAN OF JACOBSON IN THE DOG. 299 



The Okgan of Jacobson m the Dog. By E. Klein, M.D., 

 F.R.S., Joint Lecturer on General Anatomy and Phy- 

 siology in the Medical School of St. Bartholomew's 

 Hospital. (With Plate XXVI.) 



In my previous memoirs ^ the general arrangement and 

 structure of the organ of Jacobson in the guinea-pig and 

 rabbit, as well as the relations of the organ to the canals of 

 Stenson, were minutely described, and in the present paper 

 I propose to follow up the subject in the dog. 



Exposing the septum nasale in its front part in the animal 

 just killed we notice, close to the lower nasal furrow on each 

 side, a small projection, running parallel with the nasal 

 furrow, above it is another larger projection of the same 

 direction ; this latter curves upwards in the most anterior 

 portion of the septum, exactly above the incisor teeth, while 

 the former is at this region lost altogether. The upper 

 larger projection is a solid fold of the mucous membrane of 

 the nasal septum, while the lower one indicates the position 

 of the organ of Jacobson. 



On comparing transverse sections through this lower pro- 

 jection, which for brevity's sake we may call Jacobson's 

 projection, with transverse sections for some distance in 

 front of it, we perceive that the organ of Jacobson extends 

 considerably further in front than is indicated by the above 

 projection. 



In the guinea-pig and rabbit the projection indicating the 

 organ of Jacobson was due to the presence of the organ as a 

 whole, but in the dog this is not the case, since Jacobson's 

 projection is due partly to a peculiarity in the shape, and to 

 a peculiar prominence of the cartilage of Jacobson, as will 

 be pointed out in detail below, and not to the presence of 

 the organ as a whole. In the front part of the organ this 

 peculiarity of the cartilage is wanting, and the projection of 

 Jacobson is absent, although the organ is still continued in 



' This Journal, 1881, January, April and October. 



