Lateral Wall of the Cavum Nasi in Man. 625 



EXPLANATION OF FIGUBES 



Figs. 7 to 12 (X 10.5) Photomicrographs of frontal sections of the head of an 

 embryo aged about 43 days (Human embryo, No. 3, Cornell University series, 

 sections 406, 380, 365, 360, 350, 325). 



Note the plugging of the nares in fig. 7, and that the conchal anlages have no 

 cartilage in them at this age (figs. 8-11). The mesenchymal tissue is, however, 

 already undergoing condensation in anticipation of cartilage in the regions of the 

 nasal septum and the lateral nasal walls. Compare this condition or pre-carti- 

 lage stage with figs. 16 to 20, and with figs. 32 to 38. Note the relation of the 

 tongue to the palatal processes in figs. 8 to 12. 



The section shown in fig. 7 is the farthest ventral and that shown in fig. 12 the 

 farthest dorsal in the series. 



P. -pal., = processus palatinus; Eth.fold, = ethmoidal fold; Max. fold, = maxil- 

 lary fold. 



Fig. 13 (16.6) Drawing of a reconstruction of the lateral wall of the nasal cav- 

 ity of an embryo aged approximately 43 days (Human embryo, No. 3, Cornell 

 University series, sections 300-420 inclusive). 



Shows the vertical position of the palatal process at this time. The definitive 

 palate is not yet formed. Note also the primitive concha inferior {Max. fold) 

 and that it occupies the greater portion of the lateral wall at this early stage. 

 The primitive ethmoidal fold {Eth. fold)— the anlage of the ethmoidal conchae — 

 is very rudimentary at this time. 



Eth. fold, = ethmoidal fold; Max. fold, = maxillary fold; P. pal., = palatal 

 process. 



Fig. 14 (X 16.6) Drawing of a reconstruction of the lateral wall of the nasal 

 cavity of an embryo aged approximately 49 days (Human embryo, No. 28. Cor- 

 nell University series, slides 40-51 inclusive). 



Compare horizontal position of the palatal process with the process in fig. 13. 

 The ethmoidal region now has two folds well marked, and a rudimentary third 

 presents in the superior and dorsal portion of the lateral wall. The concha nasalis 

 inferior occupies comparatively less of the lateral wall. Ventrally it will be 

 noticed that the reconstruction does not include all of the lateral wall. The ven- 

 tral portion of the primitive palate is, therefore, not represented in the recon- 

 struction. 



Fig. 15 (X 6.6) Drawing of a reconstruction of portion of the right wall of the 

 nasal cavity of an embryo aged about 105 days (Human embryo. No. 43, Cornell 

 University series, slides 1-90 inclusive). 



The definitive palate is completed and the choana has assumed the adult posi- 

 tion. Compare this with figs. 2, 13, and 14. The ethmoidal region now presents 

 four conchae, the highest of which is not yet well differentiated. Note the marked 

 lobule in the region of the knee of the concha nasalis media. 



