BY R. BROOM. 11 



In the next succeeding planes the relation of the duct to the 

 cartilages is very similar, but the lateral cartilage is found 

 becoming shorter and broader and detaching itself from the 

 nasal septum (fig. 4). 



On reaching the plane shown in fig. 5 the nasal cavity is found 

 to be approaching the lateral cartilage, which here becomes for 

 the first time a " nasal-floor cartilage '"' proper. At its outer 

 angle it is seen sending up a process which further back is found 

 to represent the rudimentary cartilage of the nasal wall. Here 

 the naso-palatine canal is seen flattened out and about to give off 

 Jacobson's duct. The inner part or Jacobson's duct is almost 

 surrounded by cartilage. 



In figure 6 the ducts are seen separated, and a cartilaginous 

 partition passes between them. 



In the following figure the outer part of the cartilage is seen 

 detached, while the inner forms a complete investment for 

 Jacobson's duct. Between the two portions of the divided 

 lateral cartilage is found the naso-palatine canal about to open 

 into the nasal cavity. 



Behind this region the organ and its cartilages are found quite 

 to follow the ordinary mammalian form. 



It will 1)6 observed that the points in which the Horse differs 

 from the normal type are these : — (1) occlusion or absence of the 

 anterior part of the naso-palatine canal, leading to the secretion 

 from Jacobson's organ passing backwards into the nasal cavity by 

 the upper part of the naso-palatine canal; and '2) the anterior 

 processes of cartilage usually given off from the nasal-floor or 

 lateral cartilage and passing forward supporting Jacobson's duct 

 and the naso-palatine canal, here for the greater part remain 

 united with the lateral cartilage. In the absence of even a trace 

 of the canal in its anterior part, it is doubtful whether the 

 anterior cartilaginous process repi"esents Jacobson's or Stenson's 

 cartilages or a fusion of both — probably the latter. 



