778 



THE NOSE. 



are pale, and finely granular in texture, firmly adherent one to anothef, 

 and have oval corpuscles on their surface. 



The greater part of the mucous membrane of the nasal fossse is provided 

 with nerves of common sensibility, derived from branches of the fifth pair : 

 these have already been described at pp. 599, 603 and 604. 



Blood-vessels. The arteries and veins of the nose are derived from nume- 

 rous sources : those of the interior form rich plexuses of capillaries in the 

 lining membrane. The description of the arteries will be found at pp. 350, 

 356, 361 and 362 ; that of the veins at pp. 456 and 464. 



DEVELOPMENT OP THE NOSE. 



The organ of smell, as was first pointed out by V. Baer, owes its origin, like the 

 primary auditory vesicle and the crystalline lens of the eye, to a depression of the 

 integument. This depression, the primary olfactory groove, is at first encircled 

 by a uniform wall, and is unconnected with the mouth. This stage has been 

 observed by Kolliker in the human embryo of four weeks. Soon, hoAvever, by the 

 unequal growth of the surrounding parts, a groove is formed, descending from the 

 pit and passing 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 (p. 65). 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 observes 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 extremely 

 minute communication of the incisor foramen. Meanwhile, with the growth of the 

 face, the nasal fossae deepen, and the turbinated bones make their appearance as 

 processes from their walls. Observations are still wanting to determine whether the 

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

 separately formed from peripheral blastema like all other nerves, with the exception 

 of the optic. 



Fig. 537.* 

 ABC 



Fig. 537.* VIEWS OP THE HEAD OP HUMAN EMBRTOES, ILLUSTRATING: THE DEVELOPMENT 



OP THE NOSE. 



A, Head of an embryo of three weeks (from Ecker). ] f 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 j 7, 

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



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



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 branchial cleft which becomes 

 the outer part of the meatus auditorius externus. 



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

 been removed (from Kolliker). | 



?i, the external nasal apertures ; i, intermaxillary 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 pharynx. 



