iv THE SENSE OF SMELL 171 



the excitability of the olfactory cells. If the osmometric equivalent 

 (i.e. that which carries odours) of sodium chloride = 1, then that of 

 sodium carbonate = 2, that of sodium sulphate = 4, that of sodium 

 and magnesium phosphate = 6. 



The most important fact discovered by Aronsohn is that these 

 salt solutions which have been regarded as odourless have each 

 their own more or less definite smell. Vaschide came to the same 

 conclusion. 



Nagel, Haycraft, and Zwaardemaker all disputed Aronsohn's 

 statements. Zwaardemaker objected that it is impossible to expel 

 the air completely from the upper part of the nasal cavity by 

 Aronsohn's method. If any bubble of air is left the odorous 

 substance will be exhaled into it, and may excite the olfactory 

 surface in the form of gas. According to Zwaardemaker the 

 question must remain undecided till experiments on the dead 

 subject have proved the possibility of completely filling the 

 nasal cavity. 



Veress set out to solve the problem on these lines. Before 

 experimenting on the living body he made careful studies on 

 anatomical subjects, using the right nostril of a human head sawn 

 through in the middle line. In this way he was able to make 

 direct observations on the path of the fluid introduced into the 

 nose, and further sought to determine which position of the body 

 was most favourable to complete filling of the nose, and what 

 amount of fluid was necessary. He obtained good results from a 

 posture at an angle of more than 35. In his experiments on the 

 living subject he tilted the head to postures of 50 to 80. He 

 also tried to reproduce possible pathologico-anatomical modifica- 

 tions, such as displacement and thickening of the middle 

 turbinal, variations in the olfactory groove, etc. He pointed out 

 that errors may arise also from the mucus that covers the walls of 

 the nasal cavity, since this may contain bubbles of air that are not 

 removed until the mucus itself has been expelled : and he imitated 

 the mucus in his preparations with a thick solution of gum. 



After these preliminary studies on the dead body, Veress set to 

 work on the living subject. He discovered an error in Aronsohn's 

 method, owing to the fact that the dorsum of the nose formed the 

 lowest part of the nasal cavity. Veress, on the other hand, by 

 bending the upper part of the body forward, obtained a position of 

 the head in which the olfactory surface really lies lowest. Although 

 in certain positions 1 c.c. of fluid is sufficient to cover the olfactory 

 area, he used so much that the excess ran out of the nostrils. 

 He also examined the effect of an indifferent solution of sodium 

 chloride at body temperature upon the olfactory end-organs, by first 

 filling the nose with it, and then replacing this by a similar 

 solution containing the odorous substance to be investigated. 

 Veress attributes great importance to the influence of temperature, 



