Royal Society. 435 
as modern anat-omifts do, the 'Porta Communis : All the aper- 
tures or mouths of the three femi-circular du«5ts are of fuch a 
fhape as to refemble in ibme mealure the extremity of a trumpet; 
and upon carefjlly tracing the cavity of thefe femi-circular du6ls, 
it plainly appears to the naked eye, that from the middle it grows 
infenfibl'y larger towards both its extremities j theie mouths are fo 
difpofed, as \hat two of them poflcfs the upper, and two the 
lower part of the Coricba ; and the fifth is fituatcd pretty near 
the Wall chink in the bafe of the Conch^a: On that fide of the 
Secundum Veftibulum Lahyrinthi, which regards the external 
parts of the head, there are three fmall round canals, which, as 
they are infle^ed into a femi-circle, VieuJJens with modern ana- 
tomies calls femi-circular; and the better to difringuifli theie ca- 
nals, he gives them different names according to their different 
lituations'j the firft he calls the fuperior, becaufe it furrounds the 
arched reof of the Concha j the fecond, the inft-rior, becaufe it 
encompafTes its lower parts; and the third, as being fituated be- 
tween both he calls the middle canal : The fuperior femi-circular 
duc^, as foon as it comes out of the Vefllbulum, tends upwards, 
and in its way is gradually inflefted into irfelf; and^after it has 
defcribed lomething better than a lemi-circle, and ftili bending a 
little, has reached the pofterior part of the Os^ 'Petro[um, it 
joins the inferior canal ; the inferior femi-circular Ci^j^zS. ariles from 
the lower part of the Concl^a, and having defcribed fomething 
better than a femi-circle, it joins the fuperior femi circular du£^/ 
as was juft now faid ; fo that both thefe dutSs plainly become one, 
which extending itfelf oblic^uely, terminates in xhz Porta Com- 
tnunis : The middle femi-circular du^ has two diftina orifices, 
and forms no more than a femi-circle: Thefe du6ts have a very 
fmooth internal luperficies and are for the moft part round inter- 
nally, and fometimes oval : In that fide of the Veftibulum Secun- 
dum LabyrintU, which is oppofite to the three femi-circular 
du6ts, and regards the internal parts of the ^c^oW, nature has 
placed the other apartment of the labyrinth, called Cochlea-^ and 
this Vieujfens divides into two parts 3 the firft retains the name of 
Cochlea and has a cavity, which can eafily admit of a large len- 
til ; the other part is cdled the femi-oval fpiral duvt: Upon re- 
moving that branch of the Portio Mollis of the ear, which is 
fpread over the Cochlea, there is a bony fubftance, growing to 
the middle of its bafis, about a line in length, difpoled ipirally, 
and which in fome mealure is pyramidal, and therefore called the 
Nucleus Pyramidalls Cochlea ^ this Nucleus about the middle 
of its lateral part, which regards the internal parts of the fcull, 
I i i a teib 
