THE SENSE OF TASTE. 295 



and the ligaments which hold them in place in the tympanic 

 cavity. Flexibility of the joints between the ossicles prevents 

 sudden jars at the oval window, for the joint between the mal- 

 leus and incus, being saddle-shaped, unlocks whenever abnormal 

 or excessive movements are transmitted to the malleus. 



3. Blocking of the Eustachian tube. This is quite com- 

 monly a result of adenoids or it may be due simply to a catarrh 

 of the tube. The result of the block is that the pressure on the 

 tympanic cavity falls below that of the atmosphere, because of 

 absorption of oxygen into the blood, and the tympanic mem- 

 brane bulges inwards and becomes stretched so that it cannot 

 vibrate properly to the sound waves. The deafness in this case 

 is easily removed by reopening the Eustachian tube by forcing 

 air into it. This can be done by attaching a large syringe bulb 

 to one nostril, closing the other nostril, and while the patient is 

 swallowing a mouthful of water, suddenly compressing the bulb. 



The auditory distress which is experienced by a person on 

 going into compressed air (as into a caisson) is also due to dis- 

 turbance in the tympanic pressure, for it takes a few moments 

 before this reaches that on the outside. Blowing the nose usually 

 removes the distress. 



In all these conditions, the patient hears perfectly when a 

 tuning fork is applied to the skull or teeth. This is because the 

 sound vibrations are then transmitted to the cochlea through 

 the bones of the head. When the cochlea is diseased, however, 

 the tuning fork can be heard, neither when it is sounded in air 

 nor when it is applied to the skull or teeth. 



The Sense of Taste. 



Scattered over the mucous membrane of the tongue and buccal 

 cavity, and extending back into the pharynx and even into the 

 larynx, are the receptors of taste, or taste buds. They are most 

 numerous in the grooves around the circumvallate papillae at 

 the root of the tongue, and in the fungiform papillae/ Each 

 taste bud is composed of a mass of fusiform cells packed like a 

 barrel filled with staves. The staves in the center project as 

 hairs beyond those on the outside, and it is evidently by action 



