r 214 } 
pofterior part of the nofe by an elliptic orifice, a little 
prominent, turning inwards and forward, placed la- 
terally, and juft above the velum pendulum palati. 
This canal then is compofed of two diftina: cones, 
the extremities of which unite together, but their 
bafes diverge differently : it is likewife lined with a 
porous membrane, full of criptas and mucous cells, 
continued from and like to the membrane of the 
nares (r). 
When therefore we confider the ftru^ure of the 
euftachian tube, and its free communication with the 
atmofphere, we may reafonably fuppofe it fubjed to 
inflammation of its membrane, and concretion of its 
mucus, from cold, like the external meatus ; and 
although its mucus is of a very different nature, it 
is neverthelefs liable to infpiffate by heat, when its 
thinner parts are exhaled * *. 
^^om the form of this paflage we may eafily 
conceive, that an obftrudion, pretty far advanced, is 
not to be removed without difficulty, and that’ in 
proportion, as it is more or Icfs complete, the hear- 
ing will be more or lefs injured. Why then may not 
this be fufpeded, as fometimes the caufe of deaf- 
nefs? Perhaps it is not unfrequently fo: e. When 
(c) Haller in Boerh. de Auditu, pag. 378. Not. e 
Ha^er. de Auditu, §. 485, Valfalva, cap. 2. pag. 32 
Phyfiolo^Ia. 
. idem tig. 
* Morganni and others tell us, that they conftantly find the 
cavity of the tympanum in infants always much clogged with 
mucus ; and Mr, Douglas has often obferved the fame in adults, 
and IS of opinion that it is concomitant with an obftruded tube in 
general, and that the injection is equally as efFedual as if the tube 
only was obltruded. 
a pa- 
