710 THE ORGANS OF SENSE. 
The mucous lining of the tube is continuous behind with that of the tympanic 
cavity and in front with that of the naso-pharynx. It is thin in the pars ossea, 
contains few, if any, mucous glands, and is firmly fixed to the bony wall; whilst in 
the pars cartilaginea it is loose and thrown into longitudinal folds. Numerous 
mucous glands open into the tube near its pharyngeal orifice, and here also there 
exists a considerable amount of adenoid tissue, which constitutes the “tube-tonsil” — 
of Gerlach. This adenoid tissue is continuous with that of the naso-pharynx, and, — 
like it, is especially well developed in children. The lumen of the tube is lined | 
with ciliated columnar epithelium. 
The tube is opened, during deglutition, by the dilator tube and salpingo- 
pharyngeus muscles. The former springs superiorly from the cartilaginous hook of 
the tube, and blends inferiorly with the tensor palati. When the dilator tub 
contracts, the cartilaginous hook and membranous part of the tube are drawn out- 
wards and forwards. Some anatomists are inclined to the view that the entire 
tensor palati acts chiefly as a dilator of the tube, and Riidinger has named it the 
abductor tube. The salpingo-pharyngeus muscle draws downwards and back- 
wards the inner cartilaginous plate, increasing the angle between it and the outer 
plate. Some difference of opinion exists as to the precise action of the levator 
palati; probably it assists in opening the tube. 
amg oN, 
———— 
The Eustachian tube receives its blood-supply from the ascending pharyngeal artery and 
from the middle meningeal and Vidian branches of the internal maxillary artery. Its veins 
form a network which opens into the pterygoid venous plexus. The sensory nerves of the tube 
are derived from the tympanic plexus and from the pharyngeal branches of the second division of 
the fifth cranial nerve. 
The tube of the child differs considerably from that of the adult; its lumen is relatively 
wider, its direction more horizontal, and its pars ossea relatively shorter. Kunkel states that its 
pharyngeal orifice is below the level of the hard palate in the fetus; at birth it is on the 
same level as the palate, whilst at the fourth year it is 3 to 4 mm., and in the adult 10 mm., above 
it. The pharyngeal orifice forms a narrow fissure and its cartilage projects less towards the 
middle line. 
TYMPANIC OSSICLES. 
The tympanic ossicles (ossicula auditus) form an articulated column connect- 
ing the outer with the inner wall of the tympanic cavity, and are named, from 
A 
Fra, 519.—Tympanic OssicLes OF Lerr Ear (enlarged about three times). 
A, Incus, seen from the front ; B, Malleus, viewed from behind ; C, Incus, and D, Malleus, seen from inner 
aspect ; E, Stapes. 
1. Body of ineus, with articular 7. Processus brevis. 14. Facet for incus. 
surface for head of malleus. 8. Manubrium. 15. Manubrium. 
2. Processus longus. 9. Body. 16. Head. 
3. Processus lenticularis. 10. Short process. 17. Neck. 
4. Articular surface for ineus. 11. Long process. 18. Crus anterior. 
5. Head. 12. Processus longus. 19. Crus posterior. 
6. Neck. 13. Head. : 20. Footplate. 
without inwards, the malleus or hammer, the incus or anvil, and the stapes or 
stirrup. The first is attached to the inner surface of the membrana tympani; the 
last is fixed within the circumference of the oval fenestra. 
The malleus (Fig. 519, B, D), the largest of the three ossicles, has a length of 8 
to 9 mm., and consists of a head (capitulum mallei), a neck (collum mallei), and a 
handle (manubrium mallei), together with two processes, viz.: (@) processus longus 
