SKULL OF A HUMAN FETUS OF 40 MM. 411 



medial surface, in its ventral and upper portion, looks inward, but 

 as it is followed dorsally it is seen to become directed backward, 

 and also to become much narrower, so that the dorso-caudal 

 extremity even looks slightly outward, being separated from the 

 adjacent medial wall of the planum antorbitale by a perceptible 

 interval, the lower limit of the superior meatus, while its dorsal 

 edge shows a slight prominence projecting backward a short 

 distance before the lower end is reached. 



The middle meatus (figs. 12 and 16) is quite capacious — al- 

 most cavernous — in appearance. Above, it is roofed in by the 

 overhanging middle concha, and below it is delimited by the shelf- 

 like inferior concha, these two conchae meeting dorsally to 

 bound its dorsal extremity, this latter being a deep recess. Ven- 

 trally the deepest portion of the meatus is marked by a furrow, 

 which corresponds to the Sakterwulst on the lateral surface. 

 At approximately the center of the middle meatus, close to the 

 lateral wall, but separated from it by a layer of connective tissue, 

 is a small nodule of very young cartilage, surrounded, by a shell 

 of procartilage, the latter connecting the nodule dorsally with the 

 wall of the ectethmoid, which shows a prominence at this point. 

 This nodule, which is known as the cartilago meatus medii, is 

 situated at a point of the lateral wall just opposite to the pos- 

 terior maxillary process of the lateral surface (fg. 17), and is 

 surrounded by loose connective tissue. It occurs on both sides, 

 but what its significance may be is uncertain. 



At the root of the paraseptal process there may be seen a small 

 hollow, corresponding to the eminence upon the outer surface. 

 The under surface of the ventral portion of the tectmn nasi is 

 smooth, concave, and presents, laterally and above, the foramen 

 epiphaniale, aforementioned (fig. 12). 



VISCERAL ARCHES 



Only the upper two visceral arches, representing Meckel's 

 cartilage with the auditory ossicles and Reichert's cartilage, are 

 shown in the model. 



Meckel's cartilages (figs. 3^) comprise two irregularlj^ curved 

 rods, each of which passes from the ventro-lateral recess of 



