NOSE. 



735 



below the free inferior border of the septum. 

 The upper edge of the septum is firmly fixed to 

 the base of the skull, and its posterior edge 

 gradually slopes back to the upper and back 

 part of the wide cavity of the pharynx. There 

 is no appearance of a vomer ; and the nose 

 does not project upon the face. Its position is 

 marked externally by the nostrils, which are 

 elongated vertically, oval and narrow, situated 

 about three-fourths of a line from the margin of 

 the upper lip and at the like distance from each 

 other. They are not at this time closed, but 

 lead straight backwards into the common nasal 

 and oral cavity. 



In the following periods the chief changes 

 are effected by the gradual closure of the palate, 

 the fixing of the lower margin of the septum, 

 the developement of the vomer, and the growth 

 of the anterior part of the septum and of the 

 rudiments of the nasal and superior maxillary 

 bones. With these changes the nose gradually 

 becomes more prominent, and the nostrils, 

 which at first look straightforwards, are gradually 

 turned obliquely downwards, and at last are 

 directed as in the adult nearly straight down- 

 wards. During the third and fourth months, 

 according to Burdach,the nostrils are closed bya 

 fine membrane, which in the fifth month is again 

 removed. Together with the change in their 

 direction already spoken of, the septum becomes 

 narrower and the distance between them is 

 diminished. Changes perfecting these are con- 

 tinued even long after birth in the gradual 

 elevation and elongation of the bridge of the 

 nose, and in the narrowing of its base ; and it is 

 in these changes subsequent to birth that noses, 

 which present little variety in infants, acquire the 

 almost infinite diversities of form by which they 

 characterize the faces of adults. 



Physiology of the none. Most of the pur- 

 poses to which the nose is subservient in the 

 economy are described inotherarticles. [SMELL, 

 LARYNX, Mucus, FACE.] Here, however, it 

 may be considered as the first portion of the 

 respiratory passage, and as a feature character- 

 istic of the human race and of its several 

 varieties. 



The nose is the proper channel through which 

 the air is drawn into and expelled from the 

 lungs. It alone is habitually used in respi- 

 ration by most animals, and though in man the 

 mouth is as often used in breathing as the nose, 

 (and, indeed, oftener in our own climate, in 

 which, from various causes, few persons have at 

 all times both the nasal passages free,) yet it is 

 not adapted to this office so well as to be used 

 long without inconvenience. Most persons 

 must have suffered the discomfort of breathing 

 through the mouth during a few hours' sleep : 

 all its lining membrane, as well as that of the 

 fauces and of the upper part of the larynx, be- 

 comes dry, and an excretion of saliva must be 

 artificially produced before the annoyance and 

 the danger of choking can be removed. No 

 such inconvenience attends the breathing 

 through the nose for any length of time. Its 

 more extended mucous membrane supplies a 

 fluid sufficient to keep its own epithelium moist, 

 and to saturate with vapour the air which passes 



over it, so that this air does not abstract so much 

 moisture from the surface of the epiglottis and 

 the glottis as the drier air which has passed 

 through the mouth alone. 



Again, the nose is far better adapted than the 

 mouth is for the arrest of the particles of foreign 

 solid bodies which float in the air. If such 

 particles have passed through the hairs which 

 lie at the orifices of the nostrils, and which are 

 sufficiently close-set to stop even very minute 

 bodies, they are in their further course liable to 

 be caught in the irregular surfaces of the walls 

 of the nasal fossae and entangled in the moisture 

 of their lining membrane. Hence most per- 

 sons can breathe through the nose for some time 

 without inconvenience even in a cloud of dust : 

 and the nasal cavities of the horse and other 

 Mammalia are, in this respect, still better 

 adapted for the protection of the lungs. Some 

 experiments were performed in France to de- 

 termine whether great injury of the respiratory 

 passages of horses were produced by their ex- 

 posure to the dust of roads. Horses were made 

 to trot for a considerable distance in the clouds 

 of dust thrown up by the wheels of carriages 

 driven before them ; they were killed directly 

 afterwards, and not a particle of dust appeared, 

 on the closest scrutiny, to have passed beyond 

 their nasal fossse. 



The nose is further adapted to be the first 

 portion of the respiratory passage by the acute 

 and peculiar sensibility of its mucous mem- 

 brane, and by the connection of its nerves in 

 the nervous centres with the nerves of all the 

 set of respiratory muscles. Through the ol- 

 factory nerve the nose detects the impurity of 

 the air from those gases whose deleterious pro- 

 perties are indicated by odour; and its acute 

 common sensibility affords a warning of the 

 presence of any mechanical or other common 

 irritant. The act of sneezing, which in this 

 last case is excited through the already-men- 

 tioned connection of these nerves, is an ex- 

 ample of that class of half-involuntary acts* 

 which are consequent on acute sensations; .And, 

 in this respect, it is widely distinguished from 

 the other reflex acts with which it is commonly 

 classed, but which are never, or at least not 

 necessarily, connected with sensation. Every 

 one must have felt that a certain acute sensation 

 is necessary in order that a sneeze should occur; 

 and if the sensation does not arise to that cer- 

 tain degree of acuteness, the disposition to the 

 sudden forcible expiration gradually passes off, 

 though the act had been desired and had 

 seemed on the point of being accomplished. 

 In this respect sneezing is exactly analogous to 

 coughing, an act which is never thoroughly 

 effected except in consequence of a certain 

 acuteness of sensation at the glottis. And the 

 analogy is maintained in this also, that the 

 cause of irritation which produces sneezing 

 may be seated either in the nose itself, where 

 it is always felt, or in another part. In cough- 



* They may be thus called, because, though the 

 sudden and simultaneous exertion of all die mus- 

 cles concerned is involuntary, and almost inimitable, 

 yet the putting them in a positiou for that exertion 

 is always voluntary. 



