lord 
1896.] NEW YORK ACADEMY OF SCIENCES. 179 
broader than the utriculus proper and is called the sinus utricu- 
lus (sin. u.). Its position is such as to form a nearly vertical 
portion of the ear. The horizontal canal enters this sinus at 
about the middle of its posterior wall. The anterior canal 
enters the top of the sinus, which is reduced in size and some- 
what flattened in the plane of this canal. 
ReceEssus UTRIcuLwvs. 
At the anterior end of the sacculus, immediately under the 
ampulle of the anterior and horizontal canals (a. a., h. a., Fig. 1), 
and touching the anterior end of the utriculus and also a por- 
tion of the ventral wall of the utriculus, is a rounded body a 
little longer than broad and a trifle flattened dorsally. This 
rounded body is the recessus utriculus (7. u.). It communi- 
cates with the utriculus by means of the ductus-utriculi, a small 
slit in the upper inner wall of the recessus utriculus. It also 
communicates with the sacculus by a broader opening, the canalis 
recessus saccularis. The ductus-utriculi is situated just above 
the canalis recessus saccularis. 
SEMICIRCULAR CANALS. 
Arising from the sacculus and utriculus are three nearly semi- 
circular tubes. These tubes are from 1 to 14 mm. in diameter 
and very regular. Each tube is inclosed in a capsular canal. 
They arise in three distinct planes and receive their names from 
their positions. The one that lies in a vertical plane forward 
and outward is called the anterior canal. The one that lies ina 
vertical plane backward and outward is called the posterior canal. 
The third canal lies in a plane nearly horizontal to the body of 
the ear. The planes of the first and second canals make an 
angle of 107° with each other. 
The plane of the anterior canal makes an angle of 37° with 
the median plane. The plane of the posterior canal makes an 
angle of 36° with the median plane. These angles are the aver- 
ages obtained by actual measurements made after the top of the 
capsule had been removed and before the canals had been in any 
way disturbed. Out of more than twenty-five measurements, 
the greatest variations found in any angle was less than 1° ; 
very few measurements showed any variations. Fig. 6 is a 
traced copy made from a photograph of the ear and brain. It 
shows the relations of the ear to the brain and eye, also the 
angles made by the anterior and posterior canals. The third 
canal extends outward from about the center of the body 
of the ear in a plane slightly oblique to the frontal plane. 
