Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: part, close to the roof, is seen the projecting Facial Canal. Below this is the Fenestra Ovalis, occupied by the stapes. Still further down, but more anteriorly, is seen the PromonTory or projection of the cochlea, while yet further down and nearly under the fenestra ovalis is the Fenestra Rotunda, Fig. 6.—Sagittal Head Section Passing Through The Tympanic Membrane And Displaying The Middle Ear, Attic, Iter, And Mastoid Antrum. The membrane is shown cut obliquely and exposing the middle ear, in which are seen the ossicles and the chorda tympani nerve (white), Helow and behind these the facial nerve (white) is seen in sect1on. Note how the middle ear and mastoid cells are surrounded by the condyle of the jaw in front, temporo-sphenoidal lobe above, cerebellum behind, and sigmoid sinus below and behind. The jugular bulb and vein are shown in longitudinal sections (black), and the inferior dental nerve (white) in oblique section within the lower jaw. closed by a thin membrane and leading to the scala tympani. The roof, or Tegmen Tympani, situated above the upper limit of the tympanic membrane, is a very thin plate of bone, which separates the middle ear from the dura of the middle fossa. In the infant a gap exists in this roof externally, due to the Petro-squamosal Suture, which gives passage to some veins,and traces ot it may be found in the adult. Thus extension upwards of pyogenic mischief to the brain from the middle ear may very readily occur. The floor below the lower limit of the tympanic membrane and of the Eustachian tube is narrower than the roof and much thicker. It separates the middle ear from the dome of the internal jugular vein. The anterior extremity of the middle ear is tapered and is occupied above by the canal of the tensor tympani muscle and below by ...