300 DK, E. KLEIN. 



this part beneath the superficial mucous membrane. In 

 sections through the region of the posterior part of the 

 organ it is seen that the organ as a whole may be already 

 disappearing, while the projection of Jacobson is still marked, 

 owing to the peculiar shape and the persistency of Jacob- 

 son's cartilage beyond the epithelial portion of the organ of 

 Jacobson. Comparing figs. 8 and 10 this is well seen ; fig. 

 8 is a representation of a section anterior to the projection 

 of Jacobson, fig. 10, through the projection ; in both the 

 organ of Jacobson is well represented, but in fig. 10, i.e. 

 the one through the projection, a peculiar prominence of the 

 cartilage of Jacobson is noticed, to which, in part at any rate, 

 the above projection is due. 



Fig. 13, representing a section through the posterior por- 

 tion of the organ, shows still the projection, although the 

 organ of Jacobson is altogether shifted higher than the pro- 

 jection, and in a section a little behind the one represented, 

 the epithelial part of Jacobson's organ has come to an end, 

 the cartilage of Jacobson is still present, and the projection 

 is well marked. 



In a middle-sized dog the whole length of Jacobson's pro- 

 jection is between ^ and 3 centimeters. Anteriorly it loses 

 itself gradually towards the nasal opening of the naso-pala- 

 tine or Stenson's canal. About 1 centimeter behind the 

 opening of this the projection takes its start. 



In the guinea-pig and in the rabbit we have shown that 

 the tnbe or organ of Jacobson opened with its narrow 

 mouth directly into the nasal furrow (see my former papers, 

 this Journal, January, 1882), and my friend the late Dr. 

 Reuben Harvey has shown the same condition to obtain in 

 the rat, hedgehog, and kitten. But in the dog I find the 

 relations to be different, for here the tubes or organs of 

 Jacobson do not open directly into the nasal furrow. Fol- 

 lowing in transverse sections the Stenson's canals, from their 

 funnel-shaped opening into the anterior end of the nasal 

 furrow down to their oral opening situated immediately 

 behind the middle incisors and marked by a large papilla, 

 about 0*5 centimeters in diameter, it will be seen that the 

 tube or organ of Jacobson remains associated as a closed 

 tube with Stenson's canal to near the oral opening of this 

 latter, when it ultimately becomes fused with it. 



Figs. 1 to 7 show the relation of Stenson's canal of one 

 side to the organ of Jacobson of the same side, in transverse 

 sections from the opening on the surface of the palate to the 

 point at which the organ of Jacobson becomes separated 

 from Stenson's canal. In these figs, at pp the Papilla is 



