SKULL OF A HUMAN FETUS OF 40 MM. 401 



on the right side this appears as a well-marked furrow, running 

 from above downward and forward (fig. 11). In the area just 

 above the anterior paraseptal cartilage the furrow lying above 

 the lower, thickened border is somewhat deepened, and in this 

 hollow is to be found the anlage of the organ of Jacobson (figs. 11 

 and 18). 



An interesting featm'e of the mesethmoid is found about the 

 middle of its dorsal half (the part corresponding to the future 

 lamina perpendicularis of the ethmoid bone), in the'form of two 

 paired, elongated cartilages, very small in size, which lie parallel 

 with, and close to, the surface. These may be termed the 

 superior paraseptal cartilages (figs. 11 and 16), and though mature, 

 their cartilage is younger in type than that composing the adja- 

 cent septum. The cartilage on the right is somewhat the longer, 

 measuring 13 mm., the left being 11 mm., and in direction the 

 right is parallel with the caudal border of the septum, while the 

 left runs slightly upward, as w^ll as backward. The nasal 

 septum, opposite the anterior part of each cartilage, and for a 

 short distance in front of it, shows a slight swelling, and the an- 

 terior part of the paraseptal cartilage lies just lateral to and 

 somewhat below this. So closely does the paraseptal cartilage 

 lie to the nasal septum that it is difficult to make out a separation, 

 but by the aid of the high power and close examination it is seen 

 that the cartilage is separate from the septum, except at two 

 points on the right side, and one on the left. On the right side 

 the connection points are at the anterior extremity, and about 

 the middle, while on the left the sole union is at the anterior end. 

 Thus each cartilage presents a free, posteriorly projecting ex- 

 tremity. From the caudal edges of each cartilage there stretches 

 downward a sheet of young connective tissue. Figure 16 shows 

 the relationships of the superior paraseptal cartilage to this sheet, 

 and it will be seen that, where the cartilage is free from union 

 with the septum, as it is on each side in this figure, the relation- 

 ship of the cartilage to the membrane is somewhat similar to 

 that of a sesamoid bone to its tendon, for the real upper con- 

 nection of the membrane appears to be somewhat above the 

 cartilages, where it becomes continuous with the perichondrium 



