VOCAL ORGANS OF THE AMERICAN BITTERN. 
67 
Bittern emits at times, upon rising when disturbed. The sterno tra- 
cheal muscle, Figs. 2, 4, 5, 6, s and Fig. 3, k, that acts as a retractor 
for the vibrating, or tympaniform, membrane, is not particularly well 
developed. The tympaniform membrane, Figs. 2 and 5, o, although 
broad, is thick and incapable of much vibration, and finally, the bones 
which make up the body of the larynx, Fig. 2, e, and Fig. 4, 1, are short 
and on the sides, are fused together as seen in Fig. 5, a. 1 have given 
figures of the lower larynx, to show a peculiar modification for prevent- 
ing too great pressure against the inside of the bronchial tubes, by the 
distended lower portion of the gullet which passes between them. Al- 
though the air is cut off, in a great measure, from this portion, by the 
scapular attachment of the large compressing muscle, Fig. 3, t, yet there 
must be considerable inflation of this part. As seen in Fig. 4, a a. the 
bronchial tubes are considerably widened, even on the upper side, and 
below, their width is no less. On the under side of each tube, there is 
a swollen portion made up of a hard, rather fibrous substance. This is 
the portion colored pink in Figs. 2 and 6. This elevated portion comes 
in contact with the gullet and prevents it from pressing against the tym- 
paniform membrane. Fig. 2 shows the lower side of the larynx, 4 the 
upper side, 6 is the inside of the left bronchial tube, the right side being 
removed at this junction with the trachea, e. Fig. 5 shows the outside 
of the same tube. All the figures are the size of life. Other references 
not given, are as follows: m, trachea; t, beginning of slight bronchial 
muscle, best seen in Fig. 5, between m and a; c, bronchial tubes; and n, 
position of lungs. 
SUMMARY. 
1 give below a summary of the various modifications that the organs 
of the American Bittern have undergone in order to produce the pump- 
ing notes. 1 do not wish to be understood to say, that the different 
muscles given are positively new to science, but that the functions to 
which they are here applied, have never been noticed, and that they 
have become so modified in order to perform these functions, as to war- 
rant the applications which I have given them. I have never noticed 
anything of the kind among other Herons, and a pair of Least Bitterns, 
Ardetta exilis, taken at Way land, June 10th of this year, did not, upon 
careful examination, show even a rudiment of the peculiar vocal mus- 
cles, and they were about to breed. 
1. The oesophagul, enveloping muscles assume peculiar characters 
for the breeding season. They weighed, with the skin, six ounces. May 
be present in other species, for the purpose of shaking the skin of the 
