OP THE NERVUS OCTAVUS. 



A' 



ding themselves unto the basis cranii and occasioning uncontrollable 

 venal bleedings in the interior of the skull. 



The aperture is widened further by means of a pair of small 

 nibling pincers, whilst 

 the utmost care is 

 that a large 



token 



part of the bulla 

 towards the basis cra- 

 nii may remain unin- 

 jured , until at last a 

 full view is obtained 

 in the cavuin tympani. 



Here the way is 

 easily to be found. 



In the very first 

 place the operator's 

 attention is drawn to 

 the large triangular 

 orifice of the tuba 

 Eustachii in the ca- 

 vum tympani. .From 

 this orifice rises in 

 a gentle declivity the Fig. 4. 



triangular pyramid The position of tbe ar teria carotis, of the N. laryngeus superior, 



the promontory, its 

 turned 

 orifice. 



of the N. hypoglossus of the N. vagus and of the N. sympa- 

 thicus in relation to the bulla ossea. 



A art. carotis, B N. sympathicus, C N. v;igus, D Gangl. suprem. 

 colli N. cympathici, E Gangl. N. vagi, Fr. auric. N. facialis, G meat, 

 audit, osseus, H N. facialis, / bulla ossea, J N. laryng. sup., 

 K N. hypoglossus. 



apex being 



towards the 



On the basis of the 



pyramid and turned towards the operator is lying the foramen 



rotundum , whilst the foramen ovale , turned more backward , is 



not yet visible. 



This latter becomes visible only if the passage from the bulla 

 ossea to the bony auditory meatus is destroyed and the ossicles of 

 the ear are removed. The glossy white sinew of the m. stapedium, 

 lying enclosed in a spacious bony hole on the dorso- medial side of 

 the promontorium is not seen if the bony auditory meatus remains 

 uninjured and its bony hole is left unopened. The cavum tympani 

 may now be surveyed. 



a. The removal of the cochlea. 



From the orifice of the tuba Eustachii towards the foramen 

 rotundum runs the line, along which may be opened the thin 



