54 



The different parts of the concha of the ear are numbered ; 

 the external auditory meatus has been opened throughout its 

 length, showing the tympanic membrane at its end. The middle 

 ear with the three ossicles has been opened from above, whilst 

 the three semicircular canals and the cochlea have been dis- 

 sected out from the petrous portion of the temporal bone. 



240. An enlarged model of the human ear, dissected 

 to show its principal parts. 



From the Pedagogical Museum, St. Petersburg. 



E. 673. 1877. 







The concha of the ear can be removed from the wall of the 

 skull, as also the membrana tympani with the attached ossicles 

 from the middle ear. The three semicircular canals, one of 

 which has been opened to show the membranous canal within it, 

 and the cochlea, the lamina spiralis of which is exposed, can be 

 separately taken out of their places in the petrous portion of the 

 temporal bone. 



241. Model to illustrate the action of the membrana 

 tympani and the auditory ossicles. 



E. 13. 1881. Made by H. Sittel, Heidelberg. 



The membrana tympani is represented by a piece of leather 

 stretched over a circular hole in a vertical board, models of 

 the ossicles are in relation with it, and their axes of rotation are 

 fixed by tight strings. The stapes fits into an oval hole in a 

 parallel board, and there is a long lever which indicates and 

 magnifies its movements. On the back is a drum with caoutchouc 

 sides by which pressure can be made upon the membrana 

 tympani. 



242. Model of a human molar tooth, enlarged. 



From the Pedagogical Museum, St. Petersburg. 

 E. 677. 1877. 



The model can be separated into two halves so as to show the 

 dentine, enamel, pulp, and the vessels and nerves. 



ii. Comparative Anatomy and Systematic Zoology. 



243. Professor Cunningham's models illustrative of 

 cranio-cerebral topography and brain growth. 



E. 19. 1890. Made by L. Gasdani if Son. 



Head of a seven months' foetus. 

 Head of a newly born male child. 

 Head of a boy, 12 J years old 



