eeeepelmonic, cesophageal, and gastric 
nerves. The spinal accessory nerve (fig. 180, 
¢c) is thicker than the pneumogastric, and has 
the usual distribution. 
_ The brachial plexus is formed by the five 
terior cervical and the first dorsal nerves. 
‘he third cervical nerve is shown at g, fig. 180. 
_ The median nerve perforates the inner condyle 
of the humerus. 
_ The lumbar plexus is formed by the two 
_ posterior dorsal, the two lumbar, and the first 
_ sacral nerve. 
_. The great ischiadic nerve divides into the 
peroneal and tibial branches before it quits the 
elvis. The crural nerve is shown at h (fig. 
DIGESTIVE SYSTEM. 
Ornithorhynchus, which subsists on 
insects, larve, mollusks, and other 
invertebrates which conceal themselves 
the mud and banks of rivers, is provided 
‘with a mouth which most nearly resembles the 
flat and sensitive bill of a lamellirostral bird. 
singularly modified jaw-bones, already de- 
ibed, are invested byasmooth coriaceous inte- 
nent, (fig. 173, A, E,a,) devoid of hair, but 
forated by innumerable minute foramina. At 
base of the jaws this integument is produced 
a free fold, which overlaps the hairy covering 
the cranium immediately behind it. The 
ment covering the upper mandible ex- 
beyond the margins of the bone, and 
a tumid, smooth, and highly sensible 
the narrower and shorter under jaw is 
' closely invested: the oral or upper sur- 
of the lateral part of the under jaw sup- 
a series of about twenty nearly transverse 
‘increasing in breadth as they approach 
angle of the jaw: the corresponding sur- 
e of the upper jaw is smooth. 
The two anterior horny teeth in both jaws 
elongated, narrow, with their outer part 
d into a trenchant edge in the lower jaw. 
two posterior teeth (fig. 173, h, and F) in 
_ jaws are flat, with two broad and slight 
vations, corresponding with the two parts 
into which each molar may be divided in the 
young animal. 
_ Immediately on the outside of the posterior 
part of each molar in the lower jaw, is the orifice 
an oblong cheek-pouch (fig. 180, F, F), about 
two inches in length, and halfan inch in diame- 
ter: the pouch is continued backwards, and 
ned with a hard dry cuticle. 
The tongue (fig. 186) consists of two 
s, the normal, anterior, narrower portion 
and a broad, raised posterior lobe (/'), 
ogous to the intermolar eminence of the 
e in certain Rodents. This part is pro- 
ced anteriorly into a free projecting apex in 
the Ornithorhynchus, and is rendered still 
more remarkable in that animal by being 
armed with two short thick horny spines (g, g), 
- projecting forward. 
_ Theanterior part of the tongue is beset with 
Yather coarse papille, and extends into the 
_ posterior interspace of the incisive teeth, but 
with the apex more than an inch distant from 
pp) Toe 
» | 
hy 
4 
MONOTREMATA. 
the cloaca. 
387 
the anterior aperture of the 
mouth. The raised pos- 
terior lobe of the tongue 
must impede the passage 
of unmasticated food to 
the pharynx, and doubtless 
tends to direct it on each 
side into the cheek-pouch- 
es; whence the Ornitho- 
rhynchus may transfer its 
store at leisure to the mo- 
lar teeth, and complete its 
preparation for degluti- 
tion. An _ air-breathing 
warm - blooded animal, 
which obtains its food by 
the capture of small aqua- 
tic animals, while sub- 
merged, must derive great 
advantage from the struc- 
\ | ture which enables it to 
Q Suh 7 transfer them quickiy to 
EN a temporary receptacle, 
Nina whence they may be ex- 
i tracted and _ masticated 
i while the animal is floating 
a on the surface or at rest in 
Tongue and larynx of its burrow. 
the a The soft palate is thick, 
(Sat) broad, and divided poste- 
riorly into three fimbriated lobes. 
The pharynx is narrow, and is singularly en- 
compassed by two posterior processes of the 
thyroid cartilage (fig. 189, c,c). 
The cesophagus becomes slightly dilated near 
the diaphragm, below which it expands into a 
moderate-sized membranous stomach (fig. 187, 
1), which is chiefly remarkable for the close 
approximation of the cardiac and pyloric ori- 
fices. The intestinal canal is moderately wide, 
five feet three inches and a half in length, and 
provided, at a distance of four feet three inches 
from the pylorus, with a small and slender 
caecum (w). - 
The small intestines are chiefly remarkable 
for the extent of the mucous coat, which is 
disposed in numerous folds or valvule conni- 
ventes: these are transverse at the beginning 
of the duodenum, but are placed more or less 
obliquely in the rest of the small intestine ; 
they are about two lines broad, and placed 
very close together in the duodenum, but 
diminish in breadth and number as they ap- 
proach the coecum coli. There are about fif- 
teen longitudinal folds in the first half of the 
colon; the remainder of the intestine has a 
smooth inner surface. There is no valvula coli, 
The rectum (z) terminates at the anterior and 
dorsal part of the vestibular compartment of 
In fig. 191 a probe (6’) is passed 
through this termination. On each side of its 
termination there is an oblong glandular pro- 
minence, about four lines in length and two 
in breadth, on which there are about ten ori- 
fices of glands, which Meckel considers as 
‘analogous to the anal glands of other quadru- 
ds. 
The long, slender, tubular mouth -of the 
2c2 
