1. Keep the mouth open by a cork between the teeth. Find the papillæ
upon which open the sublingual and submaxillary ducts (pp. 223 and 224);
remove the mucosa and enlarge the opening and insert a black bristle
into either duct. Trace the duct by the bristle as far as possible on
the floor of the mouth.
2. Find the white ridge formed on the cheek by the parotid duct (p.
223). It is opposite the molar tooth, and at its cranial end the opening
of the duct is seen. Enlarge the opening and insert a black bristle as
far as possible.
3. Remove the skin and the skin-muscles from the side of the face,
beginning at the caudal end and working craniad. At the cranial border
of the carotid on the ventral side look carefully for the parotid duct
with the bristle in it. The duct is then easily traced by the removal of
the skin and muscles. Study the parotid gland (Fig. 131, 10, p. 322).
4. Remove the facial vein (Fig. 131, _b_ and _c_) and lymphatic gland
(Fig. 131, 12) covering the submaxillary gland (Fig. 131, 11) and clean
its outer surface. Raise it and find the submaxillary duct leaving its
inner surface. Reflect the digastric and mylohyoid muscles and trace the
duct to the oral mucosa. The remainder of its course is shown by the
bristle on the inside of the mouth.
5. The sublingual gland is uncovered in dissecting the submaxillary.
Its duct is seen by the side of the submaxillary. It may be pricked near
the gland and a bristle passed to its opening.
6. The infraorbital gland. Expose it by removal of the zygomatic arch
and masseter muscle. Find its duct by dissecting apart the lobules at
its ventral end. Prick the duct and insert a bristle to find its inner
opening.
7. The molar gland. Find it by raising the orbicularis oris of the
lower lip. By raising its ventral border and dissecting between it and
the mucosa the ducts may be found and perhaps pricked and bristles
inserted.
II. The mouth-cavity. Study the general description (p. 221); the lips
and the cheek. Then remove the masseter muscle and the caudal part of
the zygoma. Cut through the mandible between the first premolar and the
canine tooth. Then disarticulate the mandible, cut the cheek and also
the mylohyoid muscle and oral mucosa parallel to the medial border of
the mandible, and remove the mandible with the parts thus left attached
to it. The organs in the mouth-cavity are thus left exposed and should
be studied. To demonstrate the incisive ducts (p. 222) pass a bristle
into them.
The teeth (p. 224). These should be studied on a skull in which the
roots of the teeth have been laid bare by means of the bone-forceps, as
in Figs. 93 and 94.
The tongue (p. 226, and Fig. 95). Study its dorsal surface, the papillæ,
etc. Then dissect its _muscles_ (p. 228) from the ventral side. The
stylohyoid, digastric, and mylohyoid muscles must be removed. Then
dissect (_a_) the styloglossus (Fig. 96, _e_), (_b_) the genioglossus
(Fig. 96, _f_), (_c_) the hyoglossus (Fig. 96, _h_). Make a transverse
section of the tongue to see the intrinsic muscle-fibres.
III. The thyroid gland (p. 254, and Fig. 96, 6). Clean the sternomastoid
muscles. Cut their interdigitating portions along the median line and
reflect them. Find the lateral lobe of the thyroid gland beneath the
lateral borders of the sternohyoid muscles. Dissect it, being careful
not to destroy the delicate isthmus.
IV. The pharynx (p. 231). Remove the large lymphatic gland between the
atlantal transverse process and the larynx. Clean the outer surface of
the pharynx. Dissect the muscles of the pharynx (p. 232) as follows:
(_a_) The inferior constrictor (Fig. 96, _k_).
(_b_) The middle constrictor (Fig. 96, _j_).
(_c_) The glossopharyngeus (Fig. 96, _i_).
(_d_) The stylopharyngeus (Fig. 96, _l_).
The superior constrictor cannot well be seen at this point; it will be
examined later.
Disarticulate the cranial cornu of the hyoid from the bulla tympani and
make an incision the length of the lateral wall of the pharynx so as to
expose its cavity; study. Examine its opening into the mouth-cavity and
study the general description (p. 231). Find and study the soft palate
(p. 230). Dissect the tensor and levator palatini muscles (p. 230, and
Fig. 66, _d_ and _e_, p. 112), using, if necessary, the specimen on
which the other muscles were dissected. Then slit the soft palate
lengthwise at one side of the median line to expose the nasopharynx (p.
231). Bring the choanæ into view by use of a bit of mirror-glass. Pass a
bristle into the nares and out at the choanæ. Pass a bristle through the
Eustachian tube into the middle ear.
V. Œsophagus (p. 234). After completing the study of the pharynx, leave
the larynx and lungs in position and by displacing them toward the right
follow the œsophagus to its termination. Open it to see the folds of the
mucosa.
VI. Cut through the duodenum at its distal end and through the duodenal
mesentery so as to separate the stomach and duodenum, with the liver,
pancreas, and spleen, from the remainder of the alimentary canal. Float
the parts in a dish of water.
VII. Study the stomach (p. 234, and Fig. 97). Cut out the ventral wall
of the stomach and wash it out, so as to study its cavity, and then
continue the cut so as to expose the pyloric valve (p. 235).
VIII. Study the duodenum (p. 236). Cut away the ventral walls of the
duodenum far enough to expose the ampulla of Vater.
IX. Study the liver (p. 239, and Figs. 100 and 101). Expose the hepatic
duct of the left lateral lobe near its entrance into the lobe, and
follow it so as to expose it fully. If necessary, prick it and inflate
with blowpipe in order to follow it. Then expose the cystic duct and
other hepatic ducts and follow them to or from the common bile-duct.
Trace the latter to the duodenum. If the air does not enter any duct
readily, it may be made to do so by manipulating the duct so as to break
up the precipitated bile which obstructs it.
X. Study the pancreas (p. 241, and Fig. 102). Expose the pancreatic duct
near its entrance into the ampulla of Vater, by removing the peritoneum
from the pancreas just caudad of the end of the common bile-duct, and by
dissecting apart the pancreatic lobules until the duct appears. (If
possible, expose also the accessory duct in the same way on the ventral
side of the pancreas, two centimeters caudoventrad of the ampulla of
Vater. Prick and inflate. Trace its connection with the main duct. To
demonstrate its opening pass a bristle through an opening in it into the
duodenum.) (The pancreatic duct may be injected, if desired.)
XI. The ventral wall of the duodenum should now be removed. Cut out a
small piece, clean its mucosa with a fine brush and examine the villi
with a lens. Demonstrate the coats of the duodenal wall by stripping
them off with forceps.
XII. The ampulla of Vater (p. 236). Pass bristles through openings in
the common bile-duct and pancreatic duct into the duodenum through the
ampulla. Slice away the duodenal wall parallel to the bristles until the
bristles are exposed.