OLFACTORY NERVES. 29 



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1. In the frog, there is a fine, hair-like process projecting 

 from each cell beyond the mucous membrane, which has not 

 been observed in man or the mammalia. The great delicacy 

 of the structures entering into the composition of the olfac- 

 tory membrane renders the investigation of the termination 

 of its nervous filaments exceedingly difficult. 



Properties and Functions of the Olfactory Nerves. It 

 is almost certain that the olfactory nerves possess none of 

 the general properties of the ordinary nerves belonging to 

 the cerebro-spinal system, but that they are endowed with 

 the special sense of smell alone. As far as we know, no 

 one has exposed and operated upon the filaments coming 

 from the olfactory bulbs and distributed to the pituitary 

 membrane in living animals; but the experiments of Ma- 

 gendie upon the nerves behind the olfactory bulbs show 

 that they are entirely insensible to ordinary impressions. 

 Magendie, it is true, denied that the olfactory nerves had any 

 connection with the sense of smell, an opinion entirely un- 

 tenable and contradicted by numerous experiments and path- 

 ological observations ; but his experiments showing the insen- 

 sibility of the nerves to ordinary impressions were entirely 

 conclusive. 1 Attempts have been made to demonstrate, in 

 the human subject, the special properties of these nerves, by 

 passing a galvanic current through the nostrils ; but the situ- 

 ation of the nerves is such that these observations are of ne- 

 cessity indefinite and unsatisfactory. 2 On one or two occa- 

 sions, in witnessing surgical operations upon the upper part 

 of the nasal fossae, we have been struck with the exceedingly 

 dull sensibility of its mucous membrane. 



The question as to whether or not the olfactory nerves 

 endow the membrane of the nasal fossae with the sense of 

 smell hardly demands discussion at the present day. It must 



1 MAGENDIE, Le nerf olfactif est-il Vorgane de Vodorat ? Experiences sur cette 

 question. Journal de physiologic, Paris, 1824, tome iv., p. 169. 



a MEYER, Electricity in its Relations to Practical Medicine, New York, 1869, 

 p. 73. 



