THE AQUEDUCTS. COURSE OF THE PORTIO DURA. 479 



spheno-palatine, submaxillary, and naso-palatine, as so many 

 appendages or cranial terminations of the sympathetic nerve. 



The Aqueducts. 



It is, probably, on account of this fluid, that two small canals 

 exist ; which are called, after the anatomist who first suggested 

 their use, the Aqueducts of Cotunnius.* 



One of these commences in the scala tyrnpani of the cochlea, 

 near the foramen ovale ; and terminates in the jugular fossa, 

 by a small orifice, situated before the spine that separates the 

 eighth pair of nerves from the internal jugular vein. It is 

 called the Aqueduct of the Cochlea. 



The other originates in the vestibule, under the common 

 orifice of the two canals, and terminates on the posterior sur- 

 face of the petrous bone, by a small orifice, which is situated 

 at some distance behind the meatus auditorius internus. It is 

 called the Aqueduct of the Vestibule. 



The aqueducts of the cochlea and vestibule are large in 

 the foetus and during the growing period of the bone ; and as 

 Itard has first observed, become in old age extremely minute 

 and often entirely obliterated. The external orifice of the 

 aqueduct of the vestibule corresponds to a venous sinus (sinus 

 petrosum,) and that of the cochlea to the internal jugular 

 veins. The researches of Brugnone and Ribes have shown 

 conclusively that the aqueducts are simple foramina for the 

 introduction of veins. 



To this account of the ear it ought to be added, that the 

 Portio Dura, after entering into the petrous bone by the fora- 

 men in the upper fossa of the meatus auditorius internus, pro- 

 ceeds in a canal which is called the Aqueduct of Fallopius, 

 through the bone, to the foramen stylo-mastoideum, on its 

 inferior surface, where it emerges, and is distributed to the face. 

 It is therefore called the Facial Nerve by some anatomists. 



In the course of this nerve from the meatus through the solid 

 bone, it forms a remarkable angle, and then passes between the 



* See Sandiford's Thesaurus Dissertationum, &c., vol. i. 



