Mr. J. Jago on the Functions of the Tympanum. 299 



of the right Eustachian tube closes much less tightly than that of the 

 left, insomuch that there are times when the former becomes quite 

 patent, with no disposition to collapse. Again, having lately been 

 troubled for above five weeks with a tijmj)anic deafness, I carefully 

 registered a series of auditory phenomena resulting therefrom, and 

 found them exceedingly uotewortliy. Lastly, I have made certain 

 experiments upon the external auditory canals of the sound ears. 



I compare, then, with one another, the phenomena yielded by a 

 normal ear, an ear with an open Eustachian tube, an ear with the drum 

 impaired in a particular manner, and an ear whose external meatus is 

 in a known altered condition ; calling in facts from other sources in 

 aid ; and, finally, endeavour to determine the uses to be assigned 

 to the several structures of the drum in order to embrace all the 

 phenomena*. 



I assure myself that my Eustachian tubes are ordinarily shut, by 

 the difficulty (greater for ray left one) of forcing the breath into the 

 drums when I stop my mouth and nose, and the hinderment to its 

 escape till I swallow or eructate, showing that those acts open the 

 tubes. If we mark the sinking-in of the lachrymal sac when we swallow 

 with the mouth and nose stopped, we may see that the naso-guttural 

 cavity enlarges as the glottis is closed in that act, producing a ^xirtial 

 vacuum in the drums, and therefore from the greater barometric 

 pressure a feeling of tightness upon the membraua tympani, whilst 

 from loss of usual pressure the Eustachian tubes thereupon close more 

 finnlj', and the faucial parts swell and stick together. 



I can readily distinguish the act of opening the Eustachian tube 

 from all other guttural ones, both by hearing and feeling. A tearing 

 sound, or an irregular run of clicks, marks a slower, a sharp click a 

 quicker opening of the tube, a souffle the rush of air through the 

 patent tube, and a small crack the displacement of the membraua 

 tympani. I frequently perceive these phenomena in deglutition, 

 though, owing to the strong pressure of the current of ejected air in 

 the fauces, more especially in eructation. Sometimes also in j'awning, 

 showing that a smidering contraction of the muscles of the pharynx 

 and palate attends the opening of the tube. 



With the tube patent I feel the membraua tympani, as expiration 

 and inspiration alternate the greater amount of pressure in its two 

 surfaces, oscillating from outwards to inwards, as the inner canthus 

 of tlie eye, as reached by the nasal duct, may be seen to do. In 

 violent explosive expirations, the strength of the membrane is 

 severelj"^ tested ; the mildest speaking, coughing, or sneezing even, is 

 always disagreeably felt thereon. 



But to pass to the attendant sonorous phenomena : — the rippling 

 of the air in the tube at each elevation and dej)ression of the ribs 

 expresses itself by a souffle, and every word f utter is taken to the 

 labyrinth directly through the tube with a force that j)roves annoy- 

 ing ; — observations which plainly evince why the Eustachians are 

 u-sually impervious, and why they almost never open except at that 



* A note shows that, tliough I speak particularly from these sourees, the results 

 rest on much broa<ler grounds ; and mentions liow far anything like any portion 

 of this paper has been previously published by myself or others. 



