184 NATURE AND LIFE. 



into contact with the pituitary membrane. It is the vehi- 

 cle, the solvent, of those extremely subtile atoms which, 

 acting on the delicate fibres of the nerve, produce in it a 

 special movement, which translates itself into the most 

 varied sensations. Oxygen, and the existence in that gas 

 of a certain proportion of odorous molecules, are the two 

 essential conditions of this phenomenon. 



Such is, at least, the result of earlier experiments, and 

 of those performed of late years by Nickles. A curious 

 fact, well worthy of attention, is the remarkable diffusibility 

 and degree of subdivision exhibited by some odorous sub- 

 stances. Ambergris just thrown up on the shore spreads a 

 fragrance to a great distance, which guides the seekers 

 after that precious substance. Springs of petroleum-oil are 

 scented at a very considerable distance. Bartholin affirms 

 that the odor of rosemary at sea renders the shores of 

 Spain distinguishable long before they are in sight. So, 

 too, every one knows that a single grain of musk perfumes 

 a room for a whole year, without sensibly losing weight. 

 Haller relates that he has kept papers for forty years per- 

 fumed by a grain of amber, and that they still retained 

 the fragrance at the end of that time. He remarks that 

 every inch of their surface had been impregnated by 

 26 9 16*640 oo f one g ram of amber, and that they had per- 

 fumed for 11,600 days a film of air at least a foot in thick- 

 ness. Evidently the material quantity of the odorous prin- 

 ciple contained in a given volume of such air is so minute 

 as to elude imagination. We can readily conceive how 

 philosophers cite such instances to give a notion of the 

 divisibility of matter. 



In fact, we are now considering matter emitted by 

 odorous bodies. This shows that they do not act as cen- 

 tres of agitation, occasioning vibrations which pass in 

 waves to our organs, to exert on them a purely dynamic 

 influence. This giving off of odorous matter, with the ne- 



