284 ON THE SENSES. 



eater the nasal cavity in consequence of an inhalation. We cannot explain 

 here the mechanism of breathing ; we shall say, incidentally, only that our 

 chest resembles a pair of bellows ; when expanded by force of muscles, it receives 

 a current of air, which, like that entering through the orifices of the bellows, 

 serves to fill up the increasing space. Our bellows has two orifices, the oral 

 and the nasal cavities, we can open and close both at will, so that the air is 

 made to rush into the expanded chest either by both or one of them. At the 

 time of rcgular'and quiet breathing the oral cavity is generally closed, so that 

 the air enters the chest only through the nose, and leaves it when contracted 

 through the same; in this way light currents of atmospheric air continually pass 

 by the cuticle of the nose, and each conveys to it whatever of odorous substance 

 it has absorbed. Daily experience further teaches us that when regular, quiet 

 breathing through the nose takes place the sensations of smell are comparatively 

 faint; that their intensity increases considerably when the air is inhaled through 

 the nose by strong and rapid blasts ; that we tlius repeatedly execute short but 

 i^trong inhalations through the nose by intentional smelling or snufiing. Finally, 

 it is a well-known fact that, even in an atmosphere saturated with most intensely 

 odorous substances, we do not smell anything when inhaling the air exclu- 

 sively through the oral cavity ; though without closing our nostrils with our 

 fingers, so that the odorous air enters the nasal cavity through the open orifices, 

 but is not carried throughout it in motion. A closer analysis of these simple 

 observations leads us to correct conclusions regarding tlie conditions of smelling. 

 First, it is obvious that, together with atmospheric air, only such substances 

 reach the cuticle of the nose which can be contained in the formei-, which are 

 blended with it in an aerial form, whether they be originally gases, or changed 

 into such, in the form of steam or vapor, from a solid or liquid state. Solid or 

 liquid bodies which become gaseous at an ordinary, or only at a high tempera- 

 ture, are, as is well known, called volatile. Neither a liquid nor a solid sub- 

 stance, even if possessed of the necessary properties, can, under ordinary 

 circumstances, penetrate the nose and cause there a sensation of smell. The 

 question then arises whether there are among the non-volatile, solid or liquid, 

 bodies such as would be able, when brought in contact with the cuticle of the 

 nose, to affect the nerves of smell, it appearing probable that we only, therefore, 

 never smell the non-volatile bodies because the ordinary carrier of odorous 

 substances, the air, cannot convey them to the nose. The question can be 

 answered, and is solved by very simple experiments ; solid bodies can be blown 

 into the nasal cavity, as powders, for instance ; liquid substances can be brushed, 

 squirted, and poured into it, as we soon shall see, when it becomes manifest 

 whether they produce sensations of smell. Experiments of this kind have 

 established it as a law, which knows no exception, that oil non-volatile bodies 

 are odorless, being devoid of that unknown property which is the exciting 

 element tor the nerve of smell. Only originally gaseous or volatile substances 

 are sraellable. But that the gaseous or volatile state is not the only condition 

 which enables a substance to affect the nerve of smell is proved with certainty 

 by tlie fact already alluded to, that not all gaseous or volatile substances are 

 smcUable, as, for instance, the odorless oxygeu and carbon, and among the latter, 

 water. There must, therefore, be another condition besides the one already 

 mentioned, to render a gaseous or volatile substance odorous, and that most 

 essential condition is the great, unsolved enigma. Another question is, whether 

 the volatile or gaseous substances, which experience teaches us to be odorous, 

 can only then act excitingly on the nerves of smell when they touch the cuticle 

 of the nose in an aerial state, or whether they evince the same faculty also when 

 dissolved in water. One is inclined to expect with certainty a smelling effect 

 also in the latter case, as every odorous substance, even when coming in contact 

 with the cuticle in a gaseous state, is probably imbibed by the vesicles of the 

 epithelium, from Avhich it acts upon the nerves only after being dissolved 



