The Olfactory Organs 



297 



constitute the posterior portion of the palate and, from their fus- 

 ing borders, send projections upward to eventually reach and fuse 

 with the lower surface of the fronto-nasal process, to constitute 

 the nasal septum, dividing the nasal chamber into two distinct 

 cavities. The nasal passages are at first very short but, as the 



FlO. 34. SCHISTOCEPHALUS BiFIDUS. (Gurlt). 



nose elongates, the palatine processes from the maxillary arch 

 grow backward and, fusing on the median line, completely separ- 

 ate the oral and nasal cavities so that the latter finally open 

 posteriorly, through the posterior nares, into the pharynx. 



The upper lip is formed by a fusion of the fronto-nasal pro- 

 cesses with the maxillary arch. Aberrations in the development 

 of the anterior nares and upper lip are not rare, especially in bo- 

 vidse, where, in some instances, the processus globulares fail to 

 fuse with the maxillary processes, constituting hair lip (Schisto- 

 cephalus fissilabrus). In other instances as in Fig, 34, fis- 

 sion on the median line through the fronto-nasal process occurs, 

 so that the maxilla is divided, with the mandible curved up- 



