( 8 ) 
of which is composed of the bones of the palate, and the external 
of the maxlUaries and the jugalsf both of which rest upon a 
flexible tympanic bone, vulgarly called the square bone; (i) this 
same face or front is articulated or united to the skull above by 
elastic plates j a mode of union which always leaves some mobi- 
lity. (2) 
The horn which covers the two mandibles supplies the place 
of teeth, and is sometimes prickled in such a manner as to repre- 
sent them 5 its form, as well as that of the mandibles which support 
it, varies to infinity, according to the kind of food to which each 
species is accustomed. 
The digestion of Birds is in proportion to the activity of their 
life and the strength of their respiration. The stomach is com- 
posed of three parts : the cvop„ which is an enlargement of the 
oesophagus ; the succenturium, a membranous stomach, furnished 
within hs ceils by a multitude of glands^ the juice of which is 
imbibed by the aliments ; and the v^izzard, armed with two vigorous 
muscles, united by two tendons^ radiated and covered withinside 
by a velvet-hke cartilage. (5) The aliments are ground there^ and 
the more easily in proportion as the Birds take the precaution to 
(1) In Mammalia the os qiwAratum (see fig. 1, pi. 2) makes but 
one Avitli the temporal; Geoffrey first shewed that it was distinct in 
the 2d, 3d, and 4th Classes of Yertebrated animals. In the Genus, 
Testudo of the 3d, it appears scarcely separated, as if in the act of quit- 
tin g\}[vQ temporal. 
(2) See the skull of a Duck^ figs. 1 and 2 : the maxillary ceases at the 
small rising which indicates its articulation with \\i^jugal. The upper 
mandible being united to the skull by an elastic plate (/?. fig. 3.) like a 
very thin slip of whalebone, has the power of raising itself towards the 
forehead ; a motion impossible to the upper jaws of Mammalia. 
(3) Fig. 11 was drawn from a preparation of the inside of a common 
fowl ; CE is the cesojphagus; s the succe?iturium, and g the gizzard, 
wdiich communicates internally at cj d is the duodenum or the first 12 
inches of the intestines. The crop, or prolobus {p.), is represented 
empty; when full, it swells out like that of the Vulture, fig. 29. Fig. 6" 
is the stomach of the Heron ; fig. 5 of the Procellaria Pelagica; fig. 4 
of the Ostrich : the crop is wanting ! in each, but the succenturium is 
considerably developed. In the Heron it is confounded with the 
gizzard, which, how ever, is easily distinguished by its muscular fibres. 
In the Procellaria^ the succenturium is very distinct from the gizzard 
or third stomach. In the Ostrich, the stomach seems divided into two 
parts ; the upper and smaller of the two is more glandulous than the 
other. The grain or aliment remains long enough in the crop to be 
mollified by the heat and the humour (analogous to the saliva) which 
is discharged from its cells ) so that, in fact, their food is chewed there^ 
