260 Analytical Notices of Books. 
Two pairs of muscles of voice exist in but few birds, and there is 
little uniformity of structure even in those few which possess them. In 
the Indian Crowned Pigeon, the second pair is formed by a slip from the 
first, passing downwards on each side along the trachea, to be inserted into 
the membrane between the lowest ring of the tube and the first ring of 
the bronchi; its action would be to shorten the portion of the tube, to 
which it is attached, and to produce tension of the membrana tympani- 
formis. Inthe Gannet the second pair is almost similarly inserted on a 
glandular substance affixed to the first bronchial ring. In the’ Wood 
Grouse the principal pair of muscles is detached from the trachea 
throughout its whole length, and is imserted into the os furcatorium ; 
from these pass off, at about the commencement of their lower third, a 
second pair, which becomes attached to the lower portion of the trachea, 
and is afterwards inserted into the sternum in the same situation as the 
true sterno-tracheal muscles. To the other pair the name of furculo- 
tracheal muscles is given. In three of the species of Ducks in which 
there exists an enlargement of the tube of the trachea, there are also two 
pairs of muscles of voice: the first, the usual sterno-tracheal muscles; 
the second, a pair inserted into the os furcatorium, and arising, in the 
Velvet Duck from the bony enlargement; in the Golden-eye, partly from 
the enlargement and partly below it; and in the Red-breasted Merganser, 
about half-way between the bulb and the inferior darynz. 
Three pairs of muscles of voice have hitherto been found only among 
the Psittacide, throughout the whole of which they are uniform in 
situation and shape. The first pair, passing down the sides of the trachea, 
are inserted upon the outside of the second pair; these arise, one on each 
side a little above the bone of divarication, and are inserted upon the 
outer and central portion of the bronchi at the fourth cartilage. The 
third pair arise from the sides of the last ring of the trachea, and are 
inserted upon the whole surface of two crescent-shaped hones attached 
by membrane to the bottom of the tube. The action of the latter is to 
enlarge the aperture; the second pair have the power of contracting it; 
while the first influence the length of the tube. 
Four pairs of muscles of voice have not yet been observed. The most 
complex structure, that in which five pairs exist, is found in all the 
Corvi, Starlings, Thrushes, Larks, Buntings, Finches, Warblers, Swal- 
