408 Nose, Pharynx and its Derivatives in Man 



angles. In an embryo of the 6th week (about 5^ weeks old), such as 

 represented by the model of embryo CXLIV, the nose seen from the 

 side, as in Fig. 8, is a rather irregular six-sided figure in outline. The 

 pedicle is relatively larger and the groove running down on its outer 

 side divides it into a horseshoe-shaped body. The triangular-shaped 

 outline previously mentioned has been almost entirely lost. The 

 anterior nares meet the main opening of the olfactory cavity, not at a 

 right angle but almost in a straight line. In the model of embryo 

 XLIII of the 6th week, but still older than the preceding embryo, the 

 nasal cavity is relatively larger and occupies more of the model. The 

 same general shape is preserved, however, as can be seen by comparing 

 Fig. 8 and Fig. 9. The posterior nares are wider and are closer to the 

 Eustachian tube. The same horseshoe-shaped folds are also prominent. 

 The angle at wdiich the nasal processes meet the mouth is here reversed 

 and instead of diverging they approach one another as they leave the 

 mouth cavity. In the nose of the oldest embryo modeled, that of a 

 7 weeks' embryo (embryo XXII), the nasal cavity is relatively much 

 increased in size and is not so angular. The relative size of the pos- 

 terior nares has increased constantly in relation to the size of the 

 anterior nares. This enlargement seems to be a progressive growth 

 in a cephalic and dorsal direction, and the result is to bring the rudi- 

 ment of the Eustachian tube and the nose closer and closer as develop- 

 ment proceeds. The folds on the lateral surface (see Fig. 10) have 

 changed somewhat, but the tendency toward the horseshoe shape de- 

 scribed in the other models is still recognizable here. From the inside, 

 Jacobson's organ appears as a small conical elevation looking dorsally, 

 and it is located near the caudal angle of the juncture of the pedicle 

 and the large nasal cavity. In this model the cavities are relatively 

 nearer to one another than in any of the models described, and seen 

 from above they tend to approach one another slightly as they leave 

 the buccal cavity. 



Salivary Glands. 



In reference to the time of appearance of the rudiments of the various 

 salivary glands there is a difference of opinion among the different 

 authors. Some of this discrepancy is no doubt due to uncertainty in 

 regard to the exact age of the different embryos studied by different 

 observers. Chievitz '' states that the submaxillary appears in an em- 



^-J. H. Chievitz : Beitrage zur Entwiclcelungsgescbicbte der Speiclieldriisen. Arch. 

 f. Anat. 11. Physiol., Anat. Abth., 188.5. 



