AUDITORY ORGAN. 375 



basilaris, opens into the vena spiralis, whicli at the same time 

 carries a part of the blood from the ganglion spirale. 



(c) The central cochlear vein drains the blood from the 

 lamina spiralis and partly from the spiral ganglion. It opens 

 into the vena auditiva internet,. 



The general relations of the arteries and veins of the 

 cochlea are shown in Fig. 273, taken from Eichler's work. 



(4) Lymph Paths in the Labyrinth. 



The ductus endolymphaticus widens out to form a flat sac 

 (saccus endolymphaticus), which lies at the posterior surface 

 of the bone, between two folds of the dura mater. It commu- 

 nicates with the subdural lymph spaces by means of fine canals. 



The perilymphatic spaces are placed in communication with 

 the subarachnoideal space mainly by means of the ductus peri- 

 lymphaticus. Besides the lymph spaces, the blood-vessels are 

 surrounded by perivascular spaces. 



(&) The Middle Ear. 



The tympanic cavity lies in the temporal bone, bounded on 

 the outside by the membrana tympani. It contains three small 

 bones or ossicles, the stapes, malleus, and incus. The entire 

 lining membrane consists of a single layer of flat cells. In the 

 region of the opening of the Eustachian tube it possesses more 

 than one layer of ciliated cells. Small alveolar glands, such 

 as have been described by some authors, occur here only 

 exceptionally. 



The mucous membrane of the Eustachian tube is covered 

 throughout its whole length with ciliated epithelial cells, which 

 are arranged in a double layer. In the cartilaginous parts 

 these cells are higher, and among them are found goblet cells. 

 The ciliary movement is directed toward the pharynx. The 

 stratum proprium, which consists of a fibrillar connective tissue, 

 is united with the periosteum in the bony parts. In the carti- 

 laginous parts, on the contrary i. e., in the region of the 

 ostium pharyngeum there are mucous glands and collections 

 of leucocytes to form adenoid tissue. There are formed here 



