CHAPTER IV.

AFFECTIONS OF THE EUSTACHIAN TUBE.

THE structure of the Eustachian tube has been best investigated by Rüdinger, of Munich.* By his researches and those of others it seems established that the tube in man consists of two portions, one the chief passage, normally open only on swallowing, and the other a small tube-situated at the upper part, and bounded off by a rim of cartilage-which is practically pervious to air, acting probably as a "weak valve;" a view suggested, tho' with less minuteness, long ago by Dr. Wharton Jones (Fig. 6). This upper portion of the tube appears to permit the entrance and exit of air to and from the tympanum to a small extent during respiration, in some cases in which the nasal mucous membrane is much swollen; the passage of the air may sometimes be plainly heard, and thinned parts of the membrane, when these exist, may be seen to move in and out. But that in the normal state the interchange of air thus effected must be very slow, is shown by the injurious effects of greatly increased air pressure even in the healthy, unless the precaution of swallowing or inflating the drum is taken. Many instances of rupture of

* See his Atlas des Menschlichen Gehörorgans.

the membrane from such increased pressure in those employed in laying the foundations of bridges, piers, &c.,

TRANSVERSE SECTION OF THE EUSTACHIAN TUBE:-I. AT LOWER THIRD; II. AT UPPER THIRD. -1. The median cartilage bounding the tube, and terminating above in a hook-shaped process; 2 and 6. Folds of mucus membrane running along the tube at the junction of its inferior and superior portions; 4. The small canal constituting the upper part of the tube; 5. End of the hook-shaped portion of the cartilage; 7. The tensor palati, or dilator of the tube; 10. Mass of fatty tissue between the membranous portion of the tube and the tensor palati; 12. Levator palati; 14. Gland between this muscle and the basilar fibrocartilage (After Rüdinger.)

have been recorded,* but the opinion of those who have observed these cases seems to be that they do not occur * See Magnus, "Arch f. Ohr.," B. I. p. 270. Roosa, pp. 225-8.

except where there has been previous disease impeding the passage of air thro' the tube. I have met with only one case in which permanent relief to deafness ensued from exposure to compressed air; that of a youth, whose ears "opened" on going down in a diving-bell: apparently a slight case of simple closure of the Eustachian tube.

On the mode by which the opening of the tube is effected during swallowing, fresh light has been cast by the investigations of Mr. C. J. F. Yule,* who can himself voluntarily open the tube and contract the tensor tympani. The account given by him is as follows:

"It is noticed during the contraction for opening the tube: First, that the velum palati does not change either its position or shape, in fact, that it remains unmoved; and further, that it does not become tense, but hangs as soft and flaccid to the touch as at ordinary times of rest. Secondly, that the only parts that do move are the two posterior pillars of the pharynx; and their motion is ample and decided, and altogether unmistakeable. They both move inwards simultaneously towards the middle line, moving from their old position from one-half to threefourths of an inch. This action is not spasmodic, but perfectly steady, and can be sustained for some considerable time at will, the pillars maintaining their new position all the while. Now I am quite satisfied and certain that during this period the Eustachian tube is open. It

* "Journ. of Anat. and Phys.," Nov. 1873.

will be noted that from the flaccid condition of the velum, and also from the fact of its position and form remaining unaltered, the tensor and levator palati can have no participation in the opening of the tube, and that the muscles most evidently concerned are the palato pharyngei." The

CAVITY OF THE PHARYNX VIEWED FROM THE RIGHT SIDE IN MAN.-A. Hard palate. B. Velum Palati. C. Azygos Uvulæ. D. Tensor Palati. E. Levator Palati. F. Palato-pharyngeus. G. Salpyngopharyngeus uniting below with the Palato-pharyngeus. K. Lateral cartilaginous lobe of the Salpynx. L. Tendinous insertion of the Salpyngo-pharyngeus.

mode of operation is this: the salpingo pharyngeus is united at its lower attachment with the palato pharyngeus, and,

as this muscle during swallowing is drawn inwards, the salpingo pharyngeus is drawn inwards also, and so draws the projecting cartilaginous lobe of the tube, to which it is attached superiorly, away from the opposite wall. The new direction given to the salpingo pharyngeus by the movement inwards of the pillars of the fauces is the cause of the opening of the tube.* (See Fig. 7.)

From the observation of cases I am convinced that there exists a constrictor as well as a dilator of the tube; because mere mechanical irritation of the adjacent part of the fauces, as by the presence of the catheter, will sometimes evidently cause firm closure of the tube when it has before been pervious. Further evidence in the same direction is given by the fact that the vapour of chloroform will often enter an obstructed tube with ease, when air will not; and Dr. Von Tröltsch,t on anatomical grounds, asserts the existence of a constrictor of the tube; assigning this function to the levator palati. Dr. Wolf also reports that in a case of defective palate the Eustachian tube was seen to open during swallowing, and that in the act of retching it could be felt by the finger forcibly to close.

Mr. Yule confirms the statements of Drs. Jago and Rumbold respecting the effect of an abnormally open

I am indebted to the kindness of Mr. Yule and Dr. Humphry for permission to use the accompanying cut from the "Journal of Anatomy and Physiology."

† "Arch f. Ohr.,” I. p. 25.

Loc. cit.