ANATOMY OF THE ELEPHANT'S EAR. 
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and, as already stated, it is close to the back border of 
this isthmus that the canal containing what I have assumed 
to be a branch of the stylo-mastoid artery emerges. 
As shown in Fig. 3, the mouth of this canal looks very 
small. This was because it still contained the artery and 
other traversing tissues. On their removal the diameter 
of this inner opening of the canal was found to be about 4 
millimeters. The accident alluded to under the discussion 
of Fig. 2 can better be described in connection with this 
Fig. 3, as this illustration shows the specimen in its entirety. 
While making the second of the two sections intended to 
expose the Fallopian canal the bone was held firmly braced 
by pressure against its upper border and lower anterior 
corner. An increase of this pressure suddenly produced 
a crack which traversed the back part of the periotic 
and the tegmen tympani in a vertical direction, partly 
dislocating the ossicles and anteriorly tearing the mem- 
brana tympani loose from its attachment to the annulus. 
To remedy the effect of this tear I braced the membrane 
by the fine wire showm near the lower right hand corner 
of Fig. 2. This tear and the partial dislocation of the 
ossicles I regret, though less than I do another effect 
of this fracture shown but too distinctly in Fig. 4, viz., 
the tearing through, along the line of the promontory, of 
the thick membranous partition which up to that moment 
had quite separated the tympanum proper below from the 
upper chamber containing the ossicles above. In making 
further dissections, however, this same accidental fracture 
is likely to prove decidedly helpful. 
Fig. 4, though on a larger scale, is in other respects 
nearly identical with Fig. 2 of Dr. Buck's paper. In 
both the observer is supposed to be looking almost directly 
upwards towards what I may venture to term the membra- 
nous tegmen of the lower tympanum in contra-distinction 
to the bony tegmen of the upper tympanum or ossicle 
