NERVES IN THE MEMBRANA TYMPANI OF MAN 109 



hair according as the pressure stroke of the hair is increased so 

 do we pass from unpleasantness through acute pain in the ear to 

 pain radiating along the n. auriculo-temporalis. This it appears 

 to me is the impress put upon the organ through its phylogenetic 

 history that injury will entail serious results to the individual, 

 a case illustrating what Sherrington would probably call 'a selec- 

 tive adaptation attached to a specific sense of its own injuries.'" 

 As in the cornea so in the membrana tympani there is in the epi- 

 thelium but one morphological variety of nerve ending, namely, 

 free endings lying near the surface between the epithelial cells. 

 Moreover we have in the membrana tympani one other modi- 

 fied skin structure in which pain is the only species of sensation 

 which can be evoked. From this it would apjDcar that in this 

 structure there is additional support for Sherrington's hypothesis 

 that the noci-ceptive organs of the skin are probably naked nerve 

 endings. 



In a former paper ('07a) there were stated the experimental data 

 on which I based my claim that the nerve supply of the membrana 

 tympani came chiefly from the n. mandibularis through the n. 

 auriculo-temporalis and to a less extent from the n. vagus. Briefly 

 these were that in dogs and monkeys, after section of the n. man- 

 dibularis at its exit from the foramen ovale and of the n. auriculo- 

 temporalis under the mandible, degeneration was observed in the 

 nerves of the meatus acusticus externus adjacent to the membrana 

 tympani as well as in the nerves of that membrane. Recently 

 it has been asserted by Hunt that the chief nerve supply comes 

 from the gangUon geniculi of the n. facialis. The chief arguments 

 which Hunt advances in favor of this view are based on: 



1. The findings of comparative anatomy that the very consid- 

 erable afferent distribution of the facial in the lower vertebrates 

 has "in the course of phylogenetic development undergone a 

 considerable shrinkage and displacement by the n, trigeminus. 

 A vestigial remnant in the mouth is still demonstrable and an 

 important sensory innervation of facial origin still exists in the 

 middle ear and in the external ear." But there is no proof that 

 in the lower vertebrates above the cyclostomes there are sensory 



