DEVELOPMENT OF THE NOSE. 



Il8 9- 



occurs in the production of the relatively feebly developed human olfactory apparatus. 

 With this differentiation is associated the formation of the turbinates and the 

 intervening clefts (the 

 meatuses)andof theacces- Fl 



-rM-^r QI'I- rv>r>p: The <ztu H Cartilaginous capsulr 



SOry air-Spaces. J Ethmo-turbinal 



iesofZuckerkandl, Killian, 

 Schoenemann, Peter 1 and 

 others have shown that 

 the typical development of 

 the conchae proceeds from 

 three primary outgrowths 

 from the lateral nasal wall in 

 regions later correspond- 

 ing to the maxilla, ethmoid 

 and nasal bones. These 

 elevations, appropriately 

 known as the maxillo-tur- 

 binal, the ethmo-turbinal 

 and the naso-turbinal, un- 

 dergo differentiation that 

 leads to the simple or com- 

 plex definite arrangement 

 of the conchse found in 

 various animals. 



Maxillo-turbinal 



Nasal foss 

 Jacobson's organ 



Palatal process-j 

 Oral cavity 



Tongue 



Frontal section through developing nasal fossae and oral cavity which 

 communicate ; palatal processes are forming. X 15. 



In man the maxillo-turbinal, later the inferior turbinate, first appears and pre- 

 cedes the ethmo-turbinal plate that later is supplemented by a second scroll, thus 

 producing the middle and superior turbinates respectively. The naso-turbinal, 

 always rudimentary in man, is represented by a small ridge that appears in front of 

 the ethmo-turbinal and above the maxillo-turbinal plates and persists as the agger 

 nasi. The ethmo-turbinal is most intimately related to the true olfactory area and 

 undergoes, even in man, conspicuous subdivision. Although finally reduced to two 

 (the upper and middle turbinates), in the human foetus, just before birth, five ethmo- 

 turbinal plates defined by six grooves are present (Killian). Persistence in excess 

 of the usual complement accounts for the presence of the supernumerary ethmoidal 

 turbinates so often observed. 



As interpreted by Killian, the subsequent modifications of the ethmo-turbinals 

 and the intervening furrows, either by further expansion or by fusion, are not only 

 intimately concerned in producing details modelling the lateral wall of the nasal fossa, 

 as the uncinate process, ethmoidal bulla, hiatus semilunaris and infundibulum, but 

 also associated with the first appearance of the accessory air-spaces. The earliest 



establishment of these spaces pre- 



FIG. 1190. cedes the appearance of the carti- 



-Fore-brain l a g e th a t later encloses them, their 



relations to the skeleton being, 

 therefore, secondary (Kallius). 

 The ethmoidal air-cells and the 

 sphenoidal sinus are primarily con- 

 strictions from the nasal fossae, while 

 the maxillary and frontal sinuses 

 are more or less direct extensions 

 from the same cavities. 



The maxillary sinus ap- 

 pears about the middle of the third 

 fcetal month as a minute epithe- 

 lium-lined sac within the mesoblast at the side of the nasal fossa, from which it 

 has been evaginated ; by the sixth month it measures some 5 mm., and at birth 

 has acquired the size of a pea. Until the eruption of the milk teeth provides the 



Nasal aperture 

 Lateral nasal process 



Maxillary process 



Primitive choana 



' Palatal process 



Part of head of foetus 15 mm. in length, showing primitive choanae 

 and' palate. X 8. (Peter.} 



1 In Hertwig's Handbuch d. Entwikelungslehre, Lief. 4 and 5, 1902. 



