RICHARDS. 
opens on the inner surface of the specimen (seen in 
Fig. 3) at a point directly behind the back wall of 
the secondary tympanic cavity and opposite the junction 
between the narrower and wider portions of the latter. 
Embedded in the tough mass or chord of tissue which was 
extracted from this channel was an artery of considerable 
size, — a branch, no doubt, of the stylo-mastoid artery. At 
a point on the lower and anterior wall of the facial canal, 
on a line with the opening of this large arterial channel, a 
small branch of the facial nerve enters the bone in a direc- 
tion leading toward the upper tympanum. This I take to be 
the chorda tympani nerve. Its ragged end is indistinctly 
seen in the illustration projecting into the facial canal just at 
the beginning of its narrower portion. Immediately below 
this nerve tag on the cut surface of the septum between Fal- 
lopian and auditoiy canals is seen an opening some three 
or four millimeters wide. This is a cross section, close to 
its outer extremity, of the first of the two channels leading 
from the second "stall" described by Dr. Buck, — a chan- 
nel by him ascertained to have a length of 33 millimeters. 
What looks like a large cell near the lower left hand corner 
of the illustration is a cross section of the "single passage 
without any bifurcations" and measuring nearly TO milli- 
meters in length, which Dr. Buck found leading outwards 
from the third of the four "stalls." The tympanic mouths 
of these stalls are shown indistinctly in Fig. 3 of Dr. Buck's 
paper and somewhat more distinctly in Fig. 3 of this paper. 
In my illustration the septa dividing them are on careful 
inspection to be made out at the bottom of a dark elon- 
gated vertical hole lying immediately to the right of, i. c. 
behind, the border of the membrana tympani. 
Again returning to Fig. 2. — I beg to call the readers 
attention to the tolerably clear view given of the cavity 
of the upper tympanum containing the ossicles. The 
heads of the hammer and anvil and their now partly 
