VOL. XXVII.] PHILOSOPHICAL TRANSACTIONS. 595 



inner grinder of the lower jaw; e the outer grinder, where the ridges and interstices of the sides of 

 the teeth are represented; h the symphysis menti. 



Fig. 5, represents the bony part of the meatus auditorius of the right ear; a the external orifice of 

 the meatus auditorius; b the processus petrosus; c the orifice where the auditory nerve enters; d the 

 meatus auditorius; e a part of the laminae, which proceed from it on each side, and by which the 

 cellules between the two tables of the skull are formed, those situated above the meatus being removed^ 

 f part of the inner table of the skull. 



Fig. 6, represents part of the meatus auditorius opened, with other parts of the imier ear; a the 

 ragged part of the bone from which the os petrosum was separated ; b the processus petrosus opened; 

 c the crena for the membrane of the tympanum; d the honey-comb cavity of the tympanum; e its 

 inner cavit}', of a smooth surface ; f its semicircular, or undulated lines; g the orifice of the aque- 

 duct; h the orifice of the portio dura of the nerve. 



Fig. 7, represents the lower surface of the os petrosum, as it was separated from the upper part of 

 the tympanum, and other parts of the inner ear; aa the ragged margin of the bone; bb the upper 

 part of the cavity of the tympanum ; c the foramen ovale; d the protuberance, wherein the labyrinth 

 and cochlea are lodged; e the orifice of the portio dura of the auditory nerve. 



Fig. 8, represents the malleolus alone in its true dimensions; 1 the protuberant head; 2 the semi- 

 circular sinus between it and the margin ; 3 the sinus, which receives the head of the incus • 4 the 

 angle below the sinus, for the head of the incus; 5 the angle where the manubrium malleoli begins- 

 6 the manubrium malleoli. 



Fig. 9, represents the incus; 1 the head of the incus j 2 the sinus, or neck of the incus- 3 two 

 apophyses; 4 a long protuberance with the sinus for the os quadrangulare at its extremity. 



Fig. 10, 11, 12, represent the stapes; 1 the small part of the stapes, where it is articulated with 

 the incus, with a sinus at its extremity, being the other half of the cavity for the os quadrangulare - 

 2 2 two small portions of the stapes, where it is articulated with the basis. 



Fig. 1 1 , the basis of the stapes separated. 



Fig. 12, the whole stapes. 



Fig. 13, the malleolus and incus joined together, with their lower side turned up; 1 the malleolus - 

 2 its articulation with the incus; 3 the incus; 4 the manubrium malleoli; 5 a point of the incus 

 formed by the other two productions; 6" the long protuberance of the incus; 7 the sinus in the extre- 

 mity of its long production. 



Fig. 14, the malleolus, incus, and stapes, articulated together; 1 the incus; 2 the malleolus; 3 

 the stapes, where it shuts up the foramen ovale. 



Fig. 15, represents the upper part of the lineae serailunares, or that side which is towards the pas- 

 sage of the auditory nerve ; a the five extremities cut off; b the linea semilunaris major; c the semi- 

 lunaris media; d the semilunaris minor, which is towards the cavity of the tympanum; e the com- 

 mon canal to the major and minor; f the major; g the media; h the cochlea. 



Fig. 17, represents the cochlea. 



Fig. 18, the vestibulum; b the third gyration, or turning; c the orifice; d the first gyration, or 

 turning opened; e the second turning; g the orifice at the top of the cochlea. 



Fig. 19, represents the seat of the brain enlarged, that the orifices for the blood-vessels and nerves 

 may be tlie more obvious; aa the inner table without its surrounding cellules; bb the anterior sinus; 

 cc the OS ethmoides, with its eminences, sulci and foramina for the olfactory nerve j d the crista 

 galli; ee the anterior eminences; ff the orifice for the optic nerve; gg the hole called the foramen 

 lacerum, through which pass the nervi motorii pathetici ophthalmici, or first branch of the fifth and 

 sixth pair; hh the second branch of the fiftli pair; ii the third branch of the fifth pair; kk the hole 

 for the artery of the dura mater; 11 the hole for the carotid artery; mm the hole for the auditory- 

 nerve; nnthe hole for the jugular vein; o the hole for the spinal marrow; pp part of the two con- 



4 G 2 



