DEVELOPMENT OF THE NOSE. 



1 43 1 



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



With this difiterentiation 

 intervening clefts (the 

 meatuses) and of the acces- 



associated the formation 



of the turbinates and the 

 1 189. 



sory air-spaces. 



The stud- 



Maxillo-turbin; 

 Nasal fossa 

 jacobson's organ 



Palatal process 

 Oral cavity 



Tongue "^ 



Frontal section through developing nasal fossae and oral cavity which 

 communicate ; palatal processes are forming. X 15. 



Fig 



Cartilaginous capsulp 

 Ethmo-turbinal 



iesof Zuckerkandl, Killian, 

 Schoenemann, Peter' and 

 others have shown that 

 the typical de\'elopment of 

 the conchse 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 maxilh-tur- 

 binal, the ethmo-turbinal 

 and the naso-turbinal, un- 

 dergo differentiation that 

 leads to the simple or com- 

 plex definite arrangement 

 of the conchae found in 

 various animals. 



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 

 undero-oes, 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- 

 cedes the appearance of the carti- 

 lage that later encloses them, their 

 relations to the skeleton being, 

 - _^,,— -..(^^ ^^_^ therefore, secondary (Kallius). 



y^ ^^^/(tj^ ^^IIl^^-^ — ' Lateral nasal process The ethmoidal air-cclls aiid the 



M ,^rifl^^H|k ^^^J^Hki^^ sphenoidal sinus are primarily con- 



^-^^^^B^lHL^ I^^^JP^Maxiiiary process strictions from theuasal 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 

 foetal 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 



Fig. I 190. 



Fore-brain 



Nasal aperture 

 Lateral nasal process 



Maxillary process 

 Primitive choana 



Palatal process 



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

 andpalate. X 8. {Pet'*.) 



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



