ORGAN OF HEARING. 117 



elastic membrane like the drum in the human ear 

 is tensely stretched*. Fabriciust and Cavalini J, in- 

 deed, term this the drum (tympanum) : Scarpa calls 

 it the window of the vestibule. But be this as it may, 

 the nerves of hearing are expanded upon the interior, 

 and are intimately connected with the antenna?. 



Ear, &c. of the crab, a a, the ears, from the base of which the antennae, 

 b b, arise ; c, the palpii. 



According to this view of the matter, the antennas 

 of crabs and lobsters, and by analogy in insects, may 

 perform something of the same office as Laennec's 

 instrument called the Stethoscope, which medical 

 men use for assisting the ear to ascertain the sounds 

 produced within the chest by breathing, speaking, 

 the beating of the heart, and other organic move- 

 ments. The stethoscope magnifies these sounds, and 

 gives facility and precision of listening. 



* Scarpa.de A\iditu, pp.' 2, 3. t Nye Skrifter, ii. 376, 



J Lehmann de Sensibus Externis, p. 26. 



