and the voice of the bird monotonous. The want of muscles
of voice will be ni'ore immediately : apparent by comparing the
representation of No. 1 of the second group of these vocal
illustrations, with those of the Raven,-with its five muscles
on each side, forming the fourth group.
The next division, or those »birds possessing but? cite pair
of muscles of voice at the inferior larynx, is by far the most
numerous, including as it dóes most of the Raptor es^ some of
the Insessores, all the Rasores, .Graliatores, and Natatores,
with a few exceptions, which will be pointed out. The
British species of these orders are the examples more particularly
referred to.
The single pair of muscles,' when one pair only,exist,. arise
from the whole outer surface,of the cricoid cartilage:,descending,
they form a sheath round the ^tipper part of the.ifebes,
afterwards, dividing and passing downwards in twot«equal -portions,
one on each side, uniformly attached to the tube, and
not quitting it till arrived,at or near the bonevof divarication^
when separating from the tube of the windpipe, theyrpasS •
outwards and downwards in distinct slips, on each side, to be
m
d ^
inserted upon each inner lateral edge of the breast-bone or
sternum ; third: group, figs* 1 and 2, front and side view.
This, pair of muscles support and strengthen the windpipe,
and serve to accommodate the tube to all the varied movements
of the neck: they influence thé length of the trachea,
as welf as that of thé bronchi®, and on account of their place
of insertion have been named 'sterno-tracheal. This pair of
muscles sometimes seSid off a small slip towards the bottom,
which ser-t eff up on the inner surface of the bone called the
'nferry-thought, Or-forked bone, and have been named in conse-
quence"fuTcufo-tTacheal; but this division do.es hot appear to
afford any adflitionahpowërs of voicbl In figures 1 and 2, letters1
« a'reler to the tube'; b b to the point of division, or bone
of divarication; c to the bronchia, and d to the elongated
muscles going off to be attached to the sternum. Another
example of two pair of mumbles-at the inferior larynx is found
in th e ‘family of th è Pigehns,,as represented in the third
'■'fig^é'lfJthis third grodp. - The second pair in this instance,
marked e^are formed 5df a pbribn ‘of the sterno-tracheal mus-
but taking a different direction. They proceed by a
*Txèrfo4r> slip, from^that point upon the tube where the first
pair of mu|fies~go off to be inserted upon the sternum down
the si^fof-the trachea, to be attached externally to the mem-
1 brarfe between the lowest ring of the tube, and the first ring
öff febronchia* as-shown in the side-view before referred to.
By their contraction they shorten the flexible portion of the
‘ t i p between their points of attachment, and produce tension
upon R membrana tympaniformis*
Among British Birds I have found no examples with three
pair, or four pair of muscles, at the inferior larynx; I proceed,
therefore, to the consideration of the most complex
organ,—that furnished with five pair;
'ï'he birds included in this division are all those of the
family of the Crows, the Starling, the Thrush tribe, the