288 DETAILED SYNTHESIS. 



726. THE CAVITY OF THE NOSE is formed of parts of 

 several bones complemented by cartilages. A partition 

 extends through the centre, dividing it into two cavi- 

 ties or nostrils, the central sides of which are smooth, 

 but upon the outsides of each a bone and two processes 

 (Turbinated) are constructed, that partially fill each nos- 

 tril, and very much increase the extent of surface present- 

 ed to the action of air ; especially in some animals that 

 hunt their prey, in which the bone is even coiled. 



727. CAVITIES CALLED SINUSES, in four different 

 bones, open into each nostril, as indicated in the descrip- 

 tion of the preceding figure. Their use is unknown. 

 They are lined by a delicate membrane that sometimes 

 pours out a watery fluid, which, when the head is bent 

 forward, will be freely discharged into the nose. Some- 

 times the fluid is, or will become, viscid. Sometimes the 

 membrane lining these cavities becomes inflamed, as 

 when a person has a cold in the head, and in other ways 

 proves troublesome. 



728. THE SKIN LINING THE NOSE is a continuation 

 of that covering it, only thinner, and the cuticular cells 

 are changed to ciliated epithelial in the lower part, and 

 to thin, pavement-shaped cells above, where the nerves 

 of smell are found. (The lining of the sinuses is continu- 

 ous with that lining the nose.) 



729. THE NERVES OF SMELL DESCEND INTO EACH 

 NOSTRIL in two bundles, through the cribriform or sieve- 

 like holes in the roof of the nose, one bundle being des- 

 tined for the lining covering the turbinated processes 

 (see 1 in the succeeding figure), the other bundle extend- 

 ing for about the same distance down the lining of the 

 partition. (See Fig. 196.) 



730. ODOROUS PARTICLES dissolved in the air and 

 floated or snuffed through the nostrils, striking upon the 

 delicate surfaces of their upper walls, permeate the thin 



726. How is - constructed? 727. What said of ? 728. What said of ? 

 729. How do ? 780. What effect produced by ? 



