COMPARATIVE ANATOMY. 
as the rell-mouse (glis esculentus), it is hardly 
discernible. The superior ligamenta glot- 
tidis, as well as the veiitriculi laryngis, are 
svantiiig in some bisulca, as the ox and 
sheep. 
Some species of mammalia have a pecu- 
liar and chai-acteristic voice; or at least 
certain tones, which ar e formed by addi- 
tional organs. Of this kfaid are certain 
tense membranes in some animals; and in 
others peculiar cavities, opening into the 
larynx, and .sometimes appearing as conti- 
nuations of the ventriculi laryngis. 
The neighing of the horse, for example, 
is etfected by a delicate and nearly falci- 
fonn membrane, which is attached by its 
middle to the thyroid cartilage, and has its 
extremities running along the external mar- 
gins of the l ima glottidis. 
The peculiar sound uttered by the a.ss is 
produced by means of a similar membrane, 
under which there is an excavation in the 
thyroid cartilage. There are moreover two 
large membranous sacs opening into the 
laiynx. 
The mule does not neigh like the mare 
by -which it, was conceived, but brays like 
the ass which begot it. It possesses exactly 
the same larynx as the latter, without any 
of the peculiar vocal organs of the mother ; 
a fact which, like many others, cannot be 
at all reconciled with the supposed pre- 
existence of previously formed germs in 
the ovarium of the mother. 
Several apes and baboons, as also the 
rein-deer, have on the front of the neck 
large single or double laryngeal sacs, of 
various forms and divisions, communicating 
with the larynx by one or two openings be- 
tween the os hyoides and thyroid cartilage. 
Some of the cercopitheci, as the C. Seni- 
culus, and beelzebub, have the middle and 
anterior part of the os hyoides formed into 
a spherical bony cavity, by which the ani- 
mals are enabled to produce those terrific 
and penetrating tones which can be heard 
at vast distances, and have gained them the 
name of the howling apes. 
The most striking peculiarity in the vocal 
organs of birds, and which belongs to all birds 
with a very few exceptions, consists in their 
possessing what is commonly called a double 
larynx, but which might be more properly 
described as a larynx, divided into two 
parts, placed at the upper and lower ends 
of the trachea. They have also two rimag 
glottidis. 
The superior, or proper rima glottidis, is 
placed at the upper end of the trachea; but 
is not furnished with an epiglottis. Thfe 
apparent want of this organ is compensated 
in several cases by the conical papill® plac-. 
ed at both sides of the rima. 
The apparatus which is chiefly concerned 
in forming the voice of birds is found in the 
inferior, or bronchial larynx. This contains 
a second rima glottidis, formed by tense 
membranes, which may be compared in 
several cases, particularly among the aquatic 
birds, to the reed at the mouth of musical 
instniments. It is furnished externally with 
certain pairs of muscles, varying in number 
in the different orders and genera; and wdth 
a kind of thyroid gland. The course and 
proportionate length of the trachea, and 
particularly the structure of the inferior 
lai-ynx, vary veiy considerably in ' the dif- 
ferent species, and even in the two sexes, 
especially among the aquatic birds. Tims’ 
for example, the tame or dumb swan (anas 
olor)hasa straight trachea; whilst in the 
male of the wild, or whistling swan (cygnus), 
this tube makes a large convolution, which 
is contained in the hollow of tlie sternum. 
In the spoonbill (Platalea leiicorodia), as 
also in the Phasianus motmot, and others, 
similar Windings of the trachea ai e found’ 
not enclosed in the sternum. The males of 
the two genera anas and mergus have at 
their inferior or bronchial larynx a bony 
cavity, which contributes to strengthen their 
voice, 
A very little compaiisonofthe mechanisiA 
of wind musical instruments with the organs 
of the voice in birds will shew how nearly 
they are allied to each other ; and it may 
be obseived, that the sound produced by 
some of the larger birds is exactly similar 
to the notes that proceed from a clarionet 
or hautboy in the hands of an untutored 
musician. The inferior glottis exactly cor- 
responds to the reed, and produces the tone 
or simple sound. The superior larynx gives, 
it utterance, as the holes of the instrument ; 
but the strength and body of the note de-’ 
pend upon the extent and capacity of the 
trachea, and the hardness and elasticity of 
its parts. The convolution and bony cells 
of the windpipe, therefore, may be com- 
pared with the turns of a French horn, and 
the divisions of a bassoon ; and they pro- 
duce the proper effects of these parts in the 
voices ot those birds in which they are 
found, 
BHAIN AND NERVES, AND, ORGANS OF 
SENSE. 
The parts subservient to the animal fnne- 
(ipns, which constituting the leading cha- 
