DEVELOPMENT OF THE NOSE. 



773 



mouth. This staple has been observed by Kolliker in the human embryo 

 of four weeks. The olfactory groove is enclosed in the anterior ex- 

 tremity of the nasal cartilages prolonged forward from the trabeculas 

 cranii (Parker). Soon, however, by the unequal growth of the sur- 

 rounding parts, the groove so formed, descending from above, passes 

 into the mouth. Thus the middle frontal process is isolated between 

 the grooves of opposite sides, while the lateral frontal process separates 

 the nostril from the eye. The maxillary lobes, growing forwards from 

 behind the eyes, complete the boundaries of the nostrils, which then 

 open into the fore part of the mouth. Kolliker observed this stage in 

 the latter half of the second month. The palate subsequently grows 

 inwards to the middle line, as has been elsewhere stated, and separates 

 the nasal from the buccal cavity ; leaving only the small communication 

 of the incisor foramen. Meanwhile, with the growth of the face, the 



Fig. 575.- 



- Views op the Head op Human Embryoes, illustrating the Development 

 OF the Nose. 



A, Head of an embi^o of three weeks (from Ecker). ^^ 1, anterior cerebral vesicle ; 

 2, middle vesicle ; 3, nasal or middle frontal process ; 4, superior maxillary process ; 5, 

 eye ; 6, inferior maxillary process or first visceral plate, and below it the first cleft ; 7, 

 8, and 9, second, third, and fourth plates and clefts. 



B, Head of an embryo of about five weeks (from Ecker). f 



1, 2, 3, and 5, the same parts as in A ; 4, the external nasal or lateral frontal process, 

 inside which is the nasal groove ; 6, the superior maxillary process ; 7, the inferior 

 maxilla ; x , the tongue seen within the mouth ; 8, the first visceral cleft which becomes 

 the outer part of the meatus auditorius externus and tynipano-eustachian passage. 



C, View of the head of an embryo of eight weeks seen from below, the lower jaw having 

 been removed (from Kolliker). * 



n, the external nasal apertures ; ?', premaxillary or incisor process, and to the outer 

 side of this the internal nasal aperture ; m, one of the palatal processes of the upper jaw, 

 which, advancing inwards from the sides, form the partition between the mouth and nose ; 

 p, common cavity of the nose, mouth, and jiharynx. 



nasal fossa3 deepen, and the turbinated bones make their appearance as 

 processes from their walls. The ethmo-turbinal cartilages are at first 

 simple, but rapidly extend themselves to take the more or less complex 

 shape which they present in different animals or in man. 



Observations are still -^anting to determine whether the olfactory nerves are 

 developed from the bulbs, and have thus a cerebral origin, or are separately 



