478 



HISTOLOGY 



apical portion. These two spiral veins unite with vestibular branches to 

 form the vena aquaeductus cochleae (Fig. 481). 3. The internal auditory 

 vein arises within the modiolus from the veins of the spiral lamina; these 

 anastomose with the spiral veins (Fig. 482). It receives branches also 

 from the acoustic nerve and from the bones, and empties "in all prob- 

 ability, into the vena spinalis anterior." 



Lymphatic spaces within the internal ear are represented by the peri- 

 lymph spaces, which communicate through the aquseductus cochleae with 



Scala tympani. Scala vestibuli.^ 



Cross section of a spiral 

 artery of the modiolus. 



..--Vena laminae spiralis. 



Ganglion "spirale. 



"Vena spiralis superior. 



Cross section of a spiral 

 'artery of the modiolus. 



Vena lamina spiralis. 



Anastomosis. 



. ^Vena spiralis inferior. 



PIG. 482. DIAGRAM OF A SECTION OF THE FIRST (BASAL) AND SECOND TURNS OF THE COCHLEA. 

 a, Vas prominens; b, vas spirale. 



the arachnoid space; the connecting structure, or "ductus perilym- 

 phaticus," is described as a lymphatic vessel. The saccus endolymph- 

 aticus, which is the dilated distal end of the endolymphatic duct, is in con- 

 tact with the dura, and there are said to be openings between it and the 

 subdural space. In the internal ear perivascular and perineural spaces 

 are found, and they probably connect with the arachnoid spaces. 



MIDDLE EAR. 



The tympanic cavity, which contains air, is lined with a mucous mem- 

 brane closely connected with the surrounding periosteum. It consists of 



