112 
RED-BREASTED MERGANSER. 
of gravel. The inner surface of the oesophagus is very smooth when 
extended, plicate when contracted, with longitudinal series of mucous 
crypts with wide apertures, which become more numerous and close 
toward the proventriculus. The glandules of the latter organ are irregu- 
larly distributed, forming a belt 14 inches in breadth. They are cylindri- 
cal, the largest being \ inch long, and 14 twelfths broad. The duodenum, 
f g, has a diameter of 74 twelfths, but beyond its curve contracts to 34 
twelfths. The intestine is convoluted into numerous folds ; its length is 5 
feet 2 inches, its diameter about 3 twelfths ; but that of the rectum -44- 
twelfths. The cceca, Fig. 2, which cpme off at the distance of 4 inches 
from the extremity, are 11 twelfths long, 24 twelfths in their greatest 
diameter, and obtuse at their extremity. 
The trachea is 114 inches long, and is remarkable for a large dilatation 
above the middle, 2 inches in length and 11 twelfths in breadth, below 
which the tube becomes i inch in diameter, afterwards enlarges to 44 
twelfths, then continues 4 twelfths, and ends in an enormous dilatation of 
an irregular form, of which the greatest diameter is 2 inches. It is com- 
posed of a bony frame, with two lateral membranous spaces. The rings 
of the trachea, 152 in number, are broad and firmly ossified, but about 30 
at the lower part are very narrow in their anterior half ; about ten are 
incorporated with the dilatation ; the contractor muscles are very large, 
expand over the sides of the dilated part, and continue downwards, becom- 
ing narrower, and ending at the commencement of the tympanum. There 
is a pair of very large cleido-tracheal muscles, and another of sterno- 
tracheal ; but there are no inferior laryngeal muscles properly so called, 
the slip from the contractor ending without reaching the last ring. The 
bronchi come off at the distance of 9 twelfths from each other, and are 
short, but wide, and composed of about 20 half rings. 
In the trachea of a female, which is of a nearly uniform diameter through- 
out, the number of rings is 150, with 10 united rings, 5 of which extend 
beyond the bone of divarication, forming the lower larynx, which has no 
remarkable dilatation. The bronchial half rings are 20. 
