516 



EMBBfOLCGY. 



The horizontal palatal processes of the upper jaw increase in .size, 



and finally their 

 free edges en- 

 counter in the 

 median plane the 

 still broad nasal 

 septum, which has 

 grown down yet 

 farther into the 

 oral cavity. Then 

 the parts men- 

 tioned begin to 

 fuse with one an- 

 other from before 

 backward. 



Two st;ig;s of 

 this process are 



embryo Pig 3 cm 



illustrated by the 

 accompanyin g 





Fig. 290. Cross section through the head of 



long, crown -rump measurement. 

 The nasal cavities are seen to be in communication with the oral 



cavity at the places designated by a * ; K, cartilage of the nasal 



septum ; m, turbinal cartilage ; J, organ of JACOB?ON' ; J', the 



place where it opens into the nasal cavity ; gf, palatal process ; 



of, maxillary process ; zl, dental r.dge. 



figures (figs. 290 



291), in which cross sections through the anterior end of two emory. 

 Pigs are repre- 

 sented. Figure 

 290 shows the 

 stage at which 



the palatal ^* ,.;.,. j 



plate (gf) of / _, ,./ I I 



the maxillary 

 process (of) 

 has advanced 

 clcse to the 

 lower margin 

 of the nasal 

 septum. Oral 

 and nasal cavi- 

 ties are still 

 in communica- 

 tion by means 

 of the very 

 narrow palatal fissure indicated by an asterisk. 



In figure 291 the fusion has taken place. In this manner the 



-4 



Fig. 231. Cross section through the head of an embryo Pig 5 cm. 



long, crown-rump measurement. 

 k, Cartilaginous nasaJ septum ; i, nasal turbinal process ; J, JACOBSON'S 



organ with jk, JACOBSON'S cartilage ; zl, dental ru'ge ; bl, covering 



bone. 



