460 Philosophical Society of London. 



is likewise found in many insects, and in some of the mol- 



liisca. 



An abstract of this part we shall thus arrange according 



to the classes adopted by Linnaeus : 



Mumwalta. Form of the ear various. In the porcupine 

 it resembles the human. The cartilage composing 

 the pinna more delicate than in man. The meatus 

 auilitorius externus, in animals whose nature leads 

 them to dive or burrow in the ground, furnislied with 

 a valve which can be opened or shut at pleasure. Ex. 

 Water shrew and mole. 



Tvmpanum in all ; membrane belonging to it, and 

 an Eustachian tube entering it, passing from the 

 iauccii, except in the Celacea, wliere it opens into the 

 bl'vving hole. 



Mast\)id cells, or some structure approaching to it, 

 in most ; cellular in the pig, divided by bony septa j 

 a mere cavity in the dog, cat, and others. 



Ossicula auditus, generally four in number, in or- 

 niihorynchus paradoxus, only two. 



Labyrinth in all quadrupeds. Cochlea, sometimes 

 3| turns. Separate in the whales. Semicircular ca- 

 nals small. 



Aves. No external ear ; feathers peculiarly disposed 

 around the meatus, which is valvular. 



Tympana communicate with each other by cellular 

 structure*. 



Membrane convex externally. Ossiculum auditus 



single, connecting the membrane with the veslibulum. 



Labyrinth. No cochlea ; hollow bony process pf 



similar conformation; semicircidar canals projecting 



from the skull. 



Jmphibia. Crocodile the only one having an external 

 meatus. [Of this the lecturer produced a beautiful 

 preparation.] Many possess tympanum. Eustachian 

 tube, and semicircular canals, as the turtle, in whom 

 the membrane is cartilaginous. A single ossiculum. 

 Frogs two ossicula. Concretions in the vestibulum. 



Pisces. Internal ear grows proportionately to the size of 

 the animal. Semicircular canals very conspicuous. 

 Concretions of a very brittle nature in the veslibulum. 



Jnsecta. Power of hearing doubted by many anatomists, 

 but proved by Minasi, Scarpa, Comparetti, and others. 

 Veslibulum discernible in the Cancer genus. Same 

 nerves as supply the aniennse. 



• The Elephant has a similar structure. 



Vermes. 



