ANATOMY OF THE ELEPHANT^ EAR. 
9 
iotic bone. This very irregularly shaped cavity measures 
2 centimeters wide in its greatest diameter and 1| centime- 
ters long in its least diameter (the anteroposterior). The 
section of the bone shown in Fig. 2 bisected it in the plane 
of the latter. It communicates by an irregularly heart- 
shaped opening 8 millimeters wide with the secondary 
tympanic cavity described by Dr. Buck. This opening is 
very distinctly shown in Fig. 2, and through it the observer 
looks directly inwards into the secondary tympanic cavity. 
There is no communication whatever between this cell 
and any of those comprised in the pneumatic system of 
the squamosal bone. Its larger part is not shown in Fig. 
8, being continued within the outer portion of the specimen 
that was removed in making the section. A branch from 
this outer and larger part sweeps half way round the Fal- 
lopian canal, and the blind extremity of this branch, (i 
millimeters in height and o millimeters in width, closely 
approaches the upper wall of the auditory canal at a point 
but a few millimeters external to the margin of the drum- 
membrane ; from the auditory canal at this point it is sepa- 
rated by a bony septum only 2 millimeters in thickness ; 
from the Fallopian canal on the upper and outer aspects of 
the latter it is separated by a mere shell of bone not more 
than \ millimeter thick. The section of the bony septum 
between the auditory canal and Fallopian canal, as seen in 
Fig. 2, passes across this septum almost precisely on a 
level with the blind end of the branch just spoken of as 
sweeping halfway round the latter canal, so that the very 
shallow cup-shaped depression formed by the end of this 
branch upon the cut surface of the septum between the 
two canals, while plainly distinguishable in the specimen 
and indistinctly so in the photograph, is not, by reason of 
the imperfections of the art of engraving, to be made out 
in the illustration. Its position on the cut surface of the 
septum is directly below the lower corner of the irregularly 
