THE ORGAN OF JACOBSON IN THE DOG. 303 



Before entering into the description of the minute struc- 

 ture of the organ, I wish to point out the relations of the 

 osseous sup[)ort of the organ in the nasal septum. 



Immediately before passing through the hone of the 

 superior maxilla, e.e. immediately behind the incisor teeth, it 

 is noticed that the osseous bit next the median line and joined 

 here by periosteum, forms a direct continuity with the rest 

 of the maxilla, see fig. 7. These median bits of bone, repre- 

 sentino" the intermaxillary bone, extend backwards as the 

 crista nasalis, and are separated from 'the rest of the jaw 

 by thick layers of fibrous tissue. 



From the point where the organ of Jacobson has entered 

 the nasal septum (fig. 8) to the hind extremity of the organ 

 it is supported on its median and lower part by the bone of 

 the crista nasalis (intermaxillary bone). As is shown in 

 figs. 8, 9, and 10, which are taken from the anterior third, 

 of the organ, the organ of Jacobson is supported on its 

 median aspect by the spongy bone of the crista nasalis, 

 these bones being joined in the middle line by a thin layer 

 of periosteum. But in the middle and hind portions of 

 the organ this osseous support is greatly increased by a 

 plate of spongy bone above, and by its becoming again joined 

 to the palatine plate of the jaw. In fig. 11 these relations 

 are easily understood ; 2 is the spongy bone which is a 

 continuation of the osseous Support shown in figs. 8, 9, 

 and 10; 1, however, is a new addition, and S is the palatine 

 pliite of the jaw. All these various bits of bone are spongy 

 in structure, and are joined to one another and to their 

 companion on the opposite side by a thin layer of vascular 

 periosteum. 



From this description and from a comparison of the 

 figures given in the present memoir with those representing 

 the organ of Jacobson in the rabbit and guinea-pig given in 

 ]ny previous papers, it is seen that the relation of the organ 

 of Jacobson to the crista nasalis or the intermaxillary bone 

 respectively, is quite different in the three animals. Cbm- 

 pare this Journal, January, 1881, Plate VII, April, Plates 

 XVI and XVII, October, Plates XXX and XXXI. 



In the description of the organ of Jacobson we shall here 

 follow the same plan as adopted in my previous memoirs, 

 viz. considering first the cartilage of Jacobson, then passing 

 on the lateral, and then to the median wall of the organ. 

 Under lateral wall we shall also here understand the wall 

 nearest to the outer surface of the nasal septum, whilst the 



VOL. XXII. NEW SER. U 



