53 



236. Model designed by Helmholtz to illustrate the 

 action of the muscles of the eye. 



E. 155. 1874. Made by H. Sittel, Heidelberg. 



Two spheres, painted to represent enlarged eyeballs, are 

 pivoted at their centres and mounted on a stand side by side. 

 Strings are attached to them in the positions of the various 

 muscles, and carried over appropriate pulleys, so that by trac- 

 tion upon them all the motions of the ej^eballs can be imitated. 



237. An enlarged model of the human ear, the diffe- 

 rent parts of which can be removed to show their form 

 and arrangement. 



Made by Montaudon (late Dr. Auzoux), Paris. 

 E. 9. 1881. 



The different parts of the concha are named, and the vessels 

 and nerves supplying them are shown. The concha as a whole 

 can be removed. The upper part of the petrous portion of the 

 temporal bone can be lifted off so as to expose the cavities of 

 the middle and inner ears. The membrana tympani with its 

 three ossicles attached can be taken from its plac^, as also that 

 part of the facial nerve which lies within the petrous bone. The 

 bony labyrinth can be taken as a whole from its place to be sub- 

 sequently separated into three parts to exhibit its internal con- 

 nexions. The cochlea is bisected down the middle to show its 

 internal canals, and parts of the bony wall of the semicircular 

 canals have been cut away to show the membranous labyrinth 

 within. The blood vessels and nerves are very accurately shown 

 throughout. 



238. An enlarged model of the human ear, with the 

 principal parts dissected out. 



Exhibited by E. M. Cameron and Son. 1879. 



Price 21. 2s. 



The membrana tympani can be seen down the external audi- 

 tory meatus ; it may be removed with the malleus and incus 

 attached to it. The stapes is seen inserted in the foramen 

 rotundum. 



The bony labyrinth can be taken out from the petrous portion 

 of the temporal bone, and a part of its wall may be removed to 

 exhibit the membranous labyrinth within and the lamina spiralis 

 of the cochlea. 



239. An enlarged model of the human ear, with the 

 principal parts dissected out. Mounted on a square 

 black wood stand, with pamphlet of instructions in 

 drawer at base. 



Exhibited by P. Zeiller, Munich. 1879. Price 31. 10s. 



