Chapter V: Muscles of the Leg and Foot (5)

A small area of the anterior part of the right face of the rumen is adherent to the adjacent surface of the abomasum. The greater part of the ventral curvature of the omasum is attached by connective tissue to the dorsal face of the abomasum.

(Adhesion of the reticulum to the diaphragm is frequently present, but is pathological; the same is true in regard to adhesion to the liver.)

INTERIOR

The cavity of the rumen is partially divided into dorsal and ventral sacs by the =pillars=; these are folds of the wall, strengthened by additional muscular fibers, and correspond with the grooves on the outside. The two most extensive ones project like shelves into the anterior and posterior ends of the cavity forming the blind sacs at either extremity; they are termed the =chief pillars=. The =anterior chief pillar= (Pila cranialis) projects obliquely backward and upward from the ventral wall, and has a thick concave free edge which is opposite to the tenth and eleventh ribs. Its width from the middle of the free edge to its anterior border is about eight to ten inches (ca. 20 to 25 cm.). It is continued on either side by the relatively narrow =longitudinal pillars=, which connect it with the posterior pillar. The =posterior pillar= (Pila caudalis) is more nearly horizontal than the anterior one, and separates the large dorsal and ventral posterior blind sacs. Its concave free border is about a hand’s breadth in front of a transverse plane through the external angles of the ilia. From it are detached three =accessory pillars= on either side; of these, two pass around the blind sacs to meet the corresponding pillars of the opposite side. They thus mark off the posterior blind sacs from the general cavity, and are termed the =coronary pillars=. It will be noticed that the ventral coronary pillar is complete, while the dorsal one is not. The other accessory pillars join the right and left longitudinal pillars. The =right longitudinal pillar= is in part double; its ventral division fades out about the middle of the surface, while the dorsal one joins the posterior chief pillar. The distance between the middles of the anterior and posterior pillars is =only= about sixteen to eighteen inches (ca. 40 to 45 cm.) in a cow of medium size. In this space the dorsal and ventral sacs communicate freely.

The anterior =dorsal blind sac= of the rumen is separated from the reticulum by an almost vertical fold formed by the apposition of the walls of the two compartments. This =rumino-reticular fold= (Pila rumino-reticularis) is opposite to the seventh rib and intercostal space. Its free upper edge is concave and forms the lower and outer margin of the large, oval =rumino-reticular orifice= (Ostium ruminoreticulare). The inner margin of the fold if continued would end about at the cardia, but there is in this region no demarcation between rumen and reticulum; hence it is termed the =atrium ventriculi= or =vestibule=.

If the rumino-reticular fold and an imaginary completion of it be
taken as the boundary between the rumen and reticulum, it will be seen
that the cardia belongs to the latter. The outer border of the
rumino-reticular fold ends above and behind the cardia, the inner one
just behind the œsophageal groove and about four to five inches lower
down. Undoubtedly food or water swallowed with a moderate degree of
force passes first into the rumen. Foreign bodies (which are commonly
swallowed by cattle) are, however, found in the reticulum.

The =cardiac orifice= is opposite the seventh rib, a little to the left of the median plane and about four inches (ca. 10 cm.) below the spine; it is not funnel-shaped.

The =mucous membrane= of the rumen is brown in color, except on the margins of the pillars, where it is pale. It is for the most part thickly studded with large papillæ, many of which are nearly half an inch (ca. 1 cm.) long. The edges of the chief pillars and a large part of the wall of the middle of the dorsal sac are, however, not papillated. The papillary arrangement is most marked in the blind sacs. The papillæ vary much in size and form; the largest are foliate, many are narrow or filiform, and others are conical or club-shaped. The mucous membrane on the inner wall of the atrium is finely wrinkled and non-papillated, while above and externally it is papillated. The papillary arrangement also extends over the edge of the rumino-reticular fold an inch or two (ca. 2 to 5 cm.).

FIG. 289.—THORACIC AND ANTERIOR ABDOMINAL VISCERA OF OX, DEEP
DISSECTION.

Most of the rumen has been removed and the left wall of the reticulum
cut away. _A._, Left pulmonary artery; _B._, left bronchus; _V. V.
V._, pulmonary veins; _b. b._, bronchial lymph glands; _L.g._,
posterior mediastinal lymph gland; _D._, termination of duodenum;
_F._, rumino-reticular fold.
]

The =œsophageal groove= (Sulcus œsophageus) is a semicanal which begins at the cardia and passes downward (ventrally) on the right wall of the reticulum to end at the reticulo-omasal orifice. It is about six or seven inches (ca. 15 to 18 cm.) in length. Its axial direction is practically vertical, but it is twisted in a spiral fashion; thus its thickened edges or lips project first backward, then to the left, and finally forward. The twist involves chiefly the left lip, and the relative positions of the lips is reversed at the ventral end.

The mucous membrane on the lips of the œsophageal groove is brown and wrinkled, like that of the atrium; in the bottom of the groove it is pale, like that of the œsophagus, marked by longitudinal folds, and presents pointed horny papillæ on the lower part.

The =reticulo-omasal orifice= (Ostium reticulo-omasicum) is situated in the right wall of the reticulum about five or six inches above the bottom of the latter. It is rounded, and is limited below and laterally by the junction of the lips of the œsophageal groove.

In the reticulum the mucous membrane is raised into folds about half an inch high, which inclose four-, five-, or six-sided spaces (Cellulæ reticuli); this peculiar arrangement suggested the scientific name, and also the popular term “honeycomb.” These cells are subdivided by smaller folds, and the bottoms are studded with pointed horny papillæ. The cells grow smaller and gradually disappear near the œsophageal groove and the edge of the rumino-reticular fold; an inch or two from the latter the mucous membrane has the papillary arrangement of the rumen. At the reticulo-omasal orifice there are peculiar horny papillæ, which are curved and resemble the claws of a small bird.

FIG. 290.—RETICULUM OF OX, FROM PHOTOGRAPH.

The specimen was cut along the greater curvature and laid open by
reflecting the anterior wall. _C_, is the cardia. The arrow points
to the reticulo-omasal orifice. The spiral twist of the œsophageal
groove was of necessity partly undone by reflecting the wall; its
lips are drawn apart, showing some of the peculiar birdclaw-like
papillæ in the lower part.
]

The cavity of the omasum is occupied to a considerable extent by about a hundred longitudinal folds, the =laminæ= (Laminæ omasi), which spring from the dorsal and lateral walls. The largest of these—a dozen or more in number—have a convex attached edge, and a ventral, free, slightly concave edge which reaches to within a short distance of the ventral wall of the sac. If these are drawn apart or a cross-section is made, it will be seen that there is a second order of shorter laminæ, and a third order still shorter; finally, there is a series of very low folds or lines. The food is pressed into thin layers in the narrow spaces between the laminæ (Recessus interlaminares), and reduced to a fine state of division by being ground down by the numerous rounded horny papillæ which stud the surfaces of the folds. The ventral wall of the omasum forms a groove (Sulcus omasi), which connects the reticulo-omasal opening with the omaso-abomasal opening; it is about three or four inches (ca. 8 to 10 cm.) long, and is directed backward and a little downward and to the right. It is free from leaves, but marked usually by slight folds and small papillæ; it forms a direct path from the reticulum to the abomasum for fluid and finely divided food. In the neck of the omasum there are thick folds, and a number of the peculiar papillæ already mentioned as occurring in the lower part of the œsophageal groove. The =omaso-abomasal orifice= (Ostium omaso-abomasicum) is oval, and is about four inches (ca. 10 cm.) long. It is bounded in front by a thick muscular pillar which fades out above on the lateral walls of the omasum. Laterally there are two folds (Valvulæ terminales), which probably prevent regurgitation of the contents of the abomasum.

The cavity of the abomasum is divided by a constriction into two areas. The first of these (fundus gland region) is lined with a soft glandular mucous membrane, which forms about a dozen large, slightly spiral folds (Plicæ spirales). The second part (pyloric region) is much narrower and resembles in appearance the corresponding region of the horse’s stomach. A small cardiac gland zone surrounds the omaso-abomasal orifice. The pyloric orifice is small and round.

FIG. 291.—MUSCULATURE OF ŒSOPHAGEAL GROOVE AND ADJACENT PART OF
STOMACH OF OX, SEEN FROM WITHIN AFTER REMOVAL OF MUCOUS MEMBRANE.

_a_, Œsophagus; _b_, inner muscular layer of atrium; _d_,
reticulo-omasal orifice; _e_, _e′_, muscle of lips of groove; _g_,
lower end of muscle of larger lip, which curves around the
reticulo-omasal orifice in part and spreads out in the inner
muscular layer of the reticulum in part; _h_, lower end of muscle of
smaller lip which in part curves around the reticulo-omasal orifice
and is in part continuous with the inner muscular layer of the
omasal groove and the omasum; _i_, inner muscular layer of
reticulum. (Ellenberger-Baum, Anat. d. Haustiere.)
]

=Structure.=—The =serous coat= invests all of the free surface of the stomach. The surface of the rumen which is attached to the dorsal abdominal wall is of course uncovered, as well as the adjacent area to which the spleen is attached. The furrows are bridged over by the peritoneum and superficial muscle-fibers, and contain fat and (in most cases) branches of the gastric arteries. The =lesser omentum= passes from the visceral surface of the liver to the right (parietal) face of the omasum and the pyloric portion of the abomasum. There is a fold between the ventral curvature of the omasum and the dorsal curvature of the abomasum. The =great omentum= is formed by the peritoneum leaving the stomach along the left longitudinal and posterior transverse furrows and the right surface of the rumen below the longitudinal furrow, also the ventral curvature of the abomasum. Its superficial (ventral) part is attached on the right to the duodenum, while the deep (dorsal) part blends with the mesentery. It conceals the greater part of the intestine on the right side, with the exception of the duodenum, and covers the ventral sac of the rumen almost entirely. It is not lace-like, as in the horse, and contains a large amount of fat in animals in good condition. The =epiploic foramen= (of Winslow) is almost sagittal in direction.

The =muscular coat of the rumen= consists of an external longitudinal, and a thicker internal circular layer. The latter forms the bulk of the chief pillars, where it is about one-half to one inch (ca. 1 to 2 cm.) thick. Scattered bundles of striped muscle-fibers radiate from the cardia in the wall of the atrium.

The =muscular coat of the reticulum= consists of two chief layers which begin and end at the œsophageal groove; they pass in a circular or oblique fashion around the sac, the fibers of the two layers crossing each other at an acute angle. The walls of the cells contain a central muscular layer. The lips of the œsophageal groove contain a thick layer of longitudinal fibers, which are largely continuous at or cross each other below the reticulo-omasal orifice. The bottom of the groove has two layers of oblique, unstriped muscle-fibers, with a variable outer layer of striped muscle continuous with that of the œsophagus.

The =muscular coat of the omasum= consists of a thin external longitudinal layer and a thick internal circular layer. At the omasal groove there is an additional inner layer of longitudinal fibers. The laminæ contain three muscular strata—a central layer of vertical fibers, flanked on either side by a layer of longitudinal fibers, which are continuous at the attached border with the muscularis mucosæ.

FIG. 292.—STOMACH OF NEW-BORN CALF, RIGHT VIEW.

The rumen is raised.
]

The =muscular coat of the abomasum= consists of longitudinal and circular layers; the latter forms a well-developed pyloric sphincter.

The =mucous membrane= of the first three divisions is destitute of glands, and is covered with a thick, stratified, squamous epithelium; the superficial part of the latter is horny, and is shed in large patches in the rumen and omasum. The =corium= (Tunica propria) is papillated. The mucous membrane of the abomasum is glandular, and corresponds to that of the right sac of the stomach of the horse. The short fundus glands occur in that part which presents the large folds, while the long pyloric glands are found in the remainder, except about the omaso-abomasal orifice, where cardiac glands occur. The mucosa of the fundus gland region is very thin as compared with that of the horse. There is a round prominence on the pyloric valve.

THE INTESTINE

The intestine of the ox lies almost entirely to the right of the median plane, chiefly in contact with the right face of the rumen. It is attached to the sublumbar region by a common mesentery.

The =small intestine= has an average length of about 130 feet (ca. 40 m.) and a diameter of about two inches (ca. 5 to 6 cm.).

The =duodenum= is about three or four feet (ca. 1 m.) in length. It passes forward to the visceral surface of the liver; here it forms, ventral to the right kidney, an =S=-shaped curve. Thence it runs backward almost to the external angle of the ilium, where it turns on itself, passes forward alongside of the terminal part of the colon, and joins the mesenteric part (jejunum) under the right kidney. It is attached to the liver by the lesser omentum, to the abomasum by the great omentum, and to the terminal part of the colon. The =bile-duct= opens in the ventral part of the =S=-shaped curve, about two feet (ca. 60 cm.) from the pylorus. The =pancreatic duct= opens about a foot (ca. 30 cm.) further back.

The remainder of the small intestine is arranged in numerous very close coils, in contact chiefly with the right face of the ventral sac of the rumen, forming a sort of festoon at the edge of the mesentery. It is not subject to much variation in position, but a few coils may find their way behind the blind sacs of the rumen to the left side.

FIG. 293.—PEYER’S PATCHES OF SMALL INTESTINE OF OX (about ⅓ natural
size).
]

The orifices of the pancreatic duct and the bile-duct are on papillæ, no diverticulum being present. There are permanent transverse folds of the mucous membrane (Plicæ circulares). Duodenal glands (of Brunner) occur in the first fifteen feet or more (4 to 5 m.), intestinal glands throughout. Peyer’s patches are larger and more distinct than in the horse, and vary greatly in size and number; in adult cattle there are eighteen to forty; in calves, twenty to fifty-eight. They usually have the form of narrow bands. Close to the ileo-cæcal valve there is always a patch, and in most cases there is also a patch on the cæcal side of the valve.

The =large intestine= is much smaller in caliber than that of the horse, has no bands, and is not sacculated. Most of it is situated between the layers of the common mesentery.

The =cæcum= is about 20 to 30 inches (ca. 50 to 60 cm.) long, 4 to 5 inches (ca. 10 to 12 cm.) wide, and has a capacity of about 2½ gallons (ca. 9 to 10 liters). It begins opposite the lower part of the eleventh rib, and extends upward and backward against the right flank; its rounded blind end is free, and lies near or in the pelvic inlet.

FIG. 294.—PROJECTION OF VISCERA OF BULL ON BODY-WALL, RIGHT SIDE.

_P._, Pylorus; _G.b._, gall-bladder; _R.K._, right kidney; _L.K._,
left kidney; _P._, (above duodenum) pancreas; _Bl._, urinary
bladder; _V.s._, vesicula seminalis; _B.g._, bulbo-urethral
(Cowper’s) gland. Costal attachment and median line of diaphragm are
indicated by dotted lines.
]

FIG. 295.—LIVER OF OX, PARIETAL SURFACE; HARDENED _in situ_.
]

The =colon= is about 35 feet (ca. 10 m.) long; its diameter is at first about the same as that of the cæcum, but diminishes to about two inches (ca. 5 cm.). Its capacity is about 6 to 8 gallons (ca. 25 to 30 liters). With the exception of its first and terminal parts, it is arranged in double elliptical coils between the layers of the mesentery; the adjacent parts are therefore alternately centripetal and centrifugal (Gyri centripetales et centrifugales). The first part (Ansa proximalis) is marked off from the cæcum only by the ileo-cæcal opening; it forms an =S=-shaped curve and is continued by the spiral part (Ansa spiralis). The coils of this are attached to each other by connective tissue, and are best seen from the inner side. The bowel gradually diminishes in caliber, and the terminal part (Ansa distalis) leaves the spiral mass, passes forward to the great mesenteric artery and turns backward between the duodenum and the initial sigmoid part. From the ventral surface of the right kidney it passes backward, forms an =S=-shaped curve near the pelvic inlet, and joins the rectum; this part is attached to the sublumbar muscles by a short mesentery, and is also attached to the dorsal part of the duodenum.

The =rectum= is somewhat shorter than that of the horse, and is usually covered with peritoneum as far back as the first coccygeal vertebra. The retroperitoneal part is surrounded by a quantity of fat. The anus is not prominent.

FIG. 296.—LIVER OF OX, LEFT MARGINAL VIEW; HARDENED _in situ_.
]

The =serous coat= is of course absent on the adherent surfaces of the spiral part of the colon. There is a large amount of fat in the mesentery. The =longitudinal muscular coat= is evenly distributed, consequently there is no sacculation of the bowel. There is a valvular mucous fold at the ileo-cæcal orifice. A Peyer’s patch occurs in the beginning of the cæcum and one in the first part of the colon.

THE LIVER

The liver lies almost entirely to the right of the median plane. Its long axis is directed obliquely downward and forward, about parallel with the median plane, and corresponds to the curvature of the right portion of the diaphragm. It is less extensive, but thicker than that of the horse. Its average weight is about 10 to 12 pounds (ca. 4.5 to 5.5 kg.).

In small subjects the weight (according to Schmaltz) varies from 6½ to
10 pounds (ca. 3 to 4.5 kg.), in large subjects from 11 to 13 pounds
(ca. 5 to 6 kg.). According to Schneider, the average weight is about
13 pounds (ca. 6 kg.)—a little over 1 per cent. of the live weight and
about 2 per cent. of the dressed carcass.

When hardened _in situ_, its configuration adapts it accurately to the structures with which it is in contact.

The =parietal surface= is convex and is for the most part applied to the right part of the diaphragm, but a small part of it is in direct contact with the last two ribs and with the flank at the lumbo-costal angle. It faces upward, forward, and to the right.

The curvature of the parietal surface is not regular. It is marked,
except in its ventral part, by a blunt oblique ridge which corresponds
to the basal border of the right lung. This prominence divides the
surface into two areas. Of these, the external one is directed
outward, is only slightly convex, and often shows impressions of the
last three ribs. The inner area presents a depression produced by the
right crus of the diaphragm, and otherwise is regularly convex and
adapted to the tendinous center and sternal portion of the diaphragm.
The falciform ligament is attached to the surface from the œsophageal
notch to the umbilical fissure.

FIG. 297.—LIVER OF YOUNG OX, VISCERAL SURFACE; HARDENED _in situ_.
]

The =visceral surface= is concave and very irregular; it presents impressions of the chief organs which are in contact with it—the omasum and reticulum. It is also related to the pancreas and duodenum.

The following markings are quite distinct on the visceral surface of
well hardened specimens: (1) The omasal impression (Impressio omasica)
is a deep central cavity below the portal fissure. (2) The reticular
impression (Impressio reticularis) is a smaller marginal depression
below the œsophageal notch and the inner part of the preceding, from
which it is separated by a rounded ridge. (3) The abomasal impression
(Impressio abomasica), present only in the calf, is produced by the
anterior part of the abomasum. It lies along the ventral part of the
surface, and is separated by ridges from the preceding impressions. It
disappears as the omasum and reticulum increase in size and displace
the abomasum from contact with the liver. (4) Shallow grooves for the
=S=-shaped portion of the duodenum (Impressio duodenalis) may be found
above and external to the portal fissure. (5) The fossa of the
gall-bladder (Fossa vesicæ felleæ) is distinct when that organ is
full. In the calf the omasal impression is small, and the abomasal one
large in correspondence with the relative sizes of these two sacs.

The =portal fissure= is a well defined rounded depression, situated dorsal to the omasal impression. It contains, besides the vessels and duct, several large hepatic lymph glands. Above and external to it a part of the pancreas is attached.

FIG. 298.—LINE DRAWING OF LIVER OF OX, VISCERAL SURFACE OF SOFT
SPECIMEN.

_L.g._, Hepatic lymph glands at portal fissure.
]

The =dorsal border= is short and thick; it extends backward a short distance beyond the upper part of the last rib. It presents the large, thick, quadrilateral =caudate lobe=, and a deep depression for the right kidney and adrenal.

The =ventral border= is short and thin and has no interlobar incisures.

The =right= (or external) =border= is marked by a small umbilical fissure, in which the ligamentum teres is attached in the young subject.

The =left border= presents the œsophageal notch below its middle. Above this it is practically median in position, and lodges the posterior vena cava, which is partially embedded in the gland. Below the notch the border extends an inch or two (ca. 2.5 to 5 cm.) to the left of the median plane opposite the ventral third of the sixth rib.

There is no left lateral ligament. The falciform ligament is usually present, but the ligamentum teres is found only in young subjects. The lesser omentum leaves the liver along a line extending from the œsophageal notch to the portal fissure. The only distinct lobe in the adult is the caudate (Processus caudatus).

FIG. 299.—PANCREAS OF OX, GASTRO-INTESTINAL SURFACE, WITH RELATED
ORGANS.

The position of some of the larger lymph glands (_l.g._) is indicated
by dotted line; also the intraglandular course of the pancreatic
duct. Probe is passed through epiploic foramen (of Winslow).
]

A =gall-bladder= (Vesica fellea) is present. This is a pear-shaped sac, four to six inches (ca. 10 to 15 cm.) long, which lies partly on the visceral surface of the liver (to which it is attached), but largely on the abdominal wall at the lower part of the eleventh or twelfth intercostal space. It may be regarded as a diverticulum of the bile-duct, enlarged to form a reservoir for the bile. Its neck is continued by the =cystic duct= (Ductus cysticus), which joins the hepatic duct at an acute angle just outside of the portal fissure, to form with it the bile-duct (Ductus choledochus). The latter is short and enters the second bend of the =S=-shaped curve of the duodenum, _i. e._, about two feet (ca. 60 cm.) from the pylorus. Several small ducts (Ductus hepato-cystici) open directly into the gall-bladder.

In the new-born calf the liver is relatively much larger than in the
adult. The visceral surface presents, below the portal fissure, a
large rounded eminence, which is caused by the presence in the
underlying gland substance of a large venous sinus into which the
umbilical and portal veins empty. A large vessel, the =ductus
venosus=, leads from this sinus directly to the posterior vena cava.
Just external to this elevation is a small but distinct lobe about two
inches long (Processus papillaris?). The umbilical fissure is deep and
partially divides the gland into two chief lobes.

THE PANCREAS

The pancreas of the ox is irregularly quadrilateral in form, and lies almost entirely to the right of the median plane. Its weight is about the same as that of the horse. Its dorsal surface is related to the crura of the diaphragm, the cœliac and anterior mesenteric arteries, and the liver. It is attached to the liver at and external to the portal fissure, and to the crura of the diaphragm. Between these adhesions it is free and forms the ventral wall of the epiploic foramen (of Winslow). On the right side it extends backward beyond the caudate lobe of the liver between the layers of the mesoduodenum; here it is in contact with the upper part of the flank at the lumbo-costal angle, and is related above to the right kidney and by its ventro-lateral border to the ventral part of the duodenum. The gastro-intestinal or ventral surface is in contact with the dorsal curvature of the rumen and the intestine. The portal vein passes through the gland. The left extremity is small; the right or posterior is wide and thin and is often divided into two branches. The duct leaves the posterior part of the ventro-lateral (or right) border and enters the duodenum about twelve inches (ca. 30 cm.) further back than the bile-duct.

FIG. 300.—SPLEEN OF OX; VISCERAL SURFACE.
]

THE SPLEEN

The spleen has an elongated, elliptical outline, both extremities being thin, rounded, and similar in size.

Its average weight is about 30 ounces (ca. 800 to 900 gm.), or about ⅙ per cent. of the body-weight. Its length is about 16 to 20 inches (ca. 40 to 50 cm.), its width about 5 to 6 inches (ca. 12 to 15 cm.), and in the middle its thickness is about an inch (ca. 2 to 3 cm.).

The =dorsal extremity= lies under the upper ends of the last two ribs; the =ventral extremity= is usually opposite the seventh or eighth rib, about a handbreadth above its junction with the cartilage. The =parietal surface= is convex, and is related to the diaphragm. The =visceral surface= is concave, and is related chiefly to the left face of the rumen, but also usually to a narrow adjacent area of the reticulum. The dorsal part is attached to the left crus of the diaphragm and the left surface of the rumen by peritoneum and connective tissue; the ventral part is free. The hilus is situated on the dorsal third of the visceral surface, near the anterior border.

About one-half of the visceral surface of the spleen is attached
directly to the rumen and is not covered by peritoneum; the line of
reflection of the latter crosses the surface obliquely, from the upper
part of the posterior border to the anterior border a little below the
middle. Similarly there is a narrow uncovered area on the upper part
of the parietal surface along the anterior border. The hilus is not a
groove, but a simple depression. When hardened _in situ_, the organ is
seen to be somewhat twisted, so that the upper part of the parietal
surface faces upward and forward, while below it is directed outward.

DIGESTIVE SYSTEM OF THE SHEEP

The =lips= are thin and mobile; the upper one is marked by a very distinct philtrum, and otherwise is not bare.

The anterior part of the =hard palate= is prominent and smooth; on the posterior part of this area there are two narrow depressions in the form of a =V=, at the deep anterior ends of which the naso-palatine ducts open. The ridges of the palate are irregular and their edges are smooth. The posterior third or rather more of the palate is not ridged and presents numerous orifices of ducts of the palatine glands. The mucous membrane is often more or less pigmented.

The mucous membrane of the =cheeks= is covered with large papillæ, many of which are long and sharp-pointed, while others are short and blunt. There is also a series of conical papillæ on the floor of the mouth under the lateral part of the tongue.

The =tongue= resembles that of the ox in form, but the tip is comparatively smooth; the papillæ here are very numerous, but short and blunt. This difference is in conformity with the dissimilarity in the mode of prehension. The prominence of the dorsum is commonly not so pronounced nor so sharply marked off in front as in the ox. The root is smooth. The mucous membrane of the dorsum is often pigmented in spots.

The dental formula is the same as that of the ox. The =incisor teeth= form a narrow and strongly curved arch. The crowns are long and narrow; their labial surfaces are strongly convex and end at a sharp edge which is used in cropping the grass. The roots are more firmly embedded than in the ox.

The =cheek teeth= resemble those of the ox. There is a thinner layer of cement, which is usually black.

The average periods of eruption of the teeth are indicated in the subjoined table.

TEETH TEMPORARY PERMANENT
I_{1}. At birth or first 1 to 1½ years
week
I_{2} First or second week 1½ to 2 years
I_{3} Second or third week 2½ to 3 years
I_{4} Third or fourth week 3½ to 4 years
──────────────────────────────────────────────────────────────
P_{1} 2 to 6 weeks. 1½ to 2 years
P_{2} „ „
P_{3} „ „
──────────────────────────────────────────────────────────────
M_{1} 3 months (lower), 5 months (upper)
M_{2} 9 to 12 months
M_{3} 1½ to 2 years

FIG. 301.—STOMACH OF SHEEP, LEFT VIEW.

From photograph of specimen hardened _in situ_. The reticulum is
somewhat contracted. Arrow points to posterior furrow between blind
sacs.
]

FIG. 302.—STOMACH OF SHEEP, RIGHT VIEW.

From photograph of specimen hardened _in situ_. Dotted line indicates
position of spleen.
]

The =salivary glands= resemble those of the ox in general, but the parotid duct crosses the surface of the masseter muscle, and opens opposite the third or fourth cheek tooth.

The =tonsil= is bean-shaped and about half an inch (ca. 12 mm.) in length. It does not project into the fauces. The mucous membrane of the latter presents two deep and very narrow tonsillar sinuses on either side.

FIG. 303.—CROSS-SECTION OF SHEEP, THROUGH NINTH THORACIC VERTEBRA,
ANTERIOR VIEW.

_1_, Cardiac orifice; _2_, œsophageal groove; _3_, rumino-reticular
orifice; _4_, rumino-reticular fold; _5_, dorsal sac of rumen; _6_,
body of ninth thoracic vertebra; _7_, vena hemiazygos; _8_, aorta;
_9_, posterior mediastinal lymph gland; _10_, _10_, crura of
diaphragm; _11_, posterior vena cava; _12_, portal vein; _R.l._,
right lung; _L.l._, left lung; _S_, spleen (cut very obliquely);
_L_, liver; _R_, reticulum (posterior wall). Arrow points to
reticulo-omasal orifice.
]

The fornix of the =pharynx= presents a median plicated fold which is a continuation of the septum nasi. The pharyngeal orifice of the Eustachian tube has the form of a crescentic slit, placed about on a level with the inferior nasal meatus. There are two large lymph glands and a number of hæmolymph glands above the pharynx.

The =œsophagus= has a lumen of about an inch when moderately distended; otherwise it resembles that of the ox.

FIG. 304.—ABDOMINAL VISCERA OF SHEEP, SUPERFICIAL VENTRAL VIEW.
]

The =stomach= is like that of the ox in its general arrangement. Its average capacity is about four gallons (ca. 15 liters). The =cardiac opening= is opposite the middle of the eighth intercostal space; it is just to the left of the median plane and about two to three inches (ca. 5 to 7 cm.) below the vertebral column. The ventral sac of the =rumen= is relatively larger and extends further to the right of the median plane than in the ox. There are no coronary pillars in the dorsal sac, but its upper part is papillated. The papillæ of the rumen are relatively =large= and somewhat tongue-like; the largest are about a fourth of an inch (ca. 6 mm.) in length. The =reticulum= is relatively larger than in the ox. Its ventral part curves more backward and less to the right than in the ox. The parietal surface extends forward as far as the sixth rib or intercostal space, and is related to the diaphragm and liver. The fundus lies on the sternal part of the diaphragm and in contact with the abomasum. The =œsophageal groove= is disposed much like that of the ox, and is about four to five inches (ca. 8 to 10 cm.) long. The =omasum= is much smaller than the reticulum, its capacity being only about one pint. It is oval and compressed laterally. It is situated almost entirely to the right of the median plane, opposite to the ninth and tenth ribs, higher than in the ox, and has no contact with the abdominal wall. It is related on the right to the liver and gall-bladder, on the left to the rumen, and below to the abomasum. The laminæ are less numerous than in the ox; in the neck which connects the omasum with the reticulum they have the form of low thick ridges, and bear long, pointed, horny papillæ. The =abomasum= is relatively larger and longer than in the ox. Its capacity is about twice that of the reticulum and averages about two quarts (ca. 1.75 to 2 liters). The blind anterior end lies almost centrally in the xiphoid region, in relation to the liver and reticulum. Its body extends backward a little below and almost parallel with the right costal arch. The pylorus is opposite the ventral end of the eleventh or twelfth intercostal space. The cells of the reticulum are much shallower than in the ox. At the reticulo-omasal opening and on the adjacent part of the laminæ of the omasum are large, pointed, horny papillæ. The number of laminæ is less than in the ox.

The general arrangement of the =intestine= is like that of the ox. The =small intestine= is about 80 feet (ca. 24 to 25 m.) long; its average diameter is about an inch (ca. 2 to 3 cm.), the caliber increasing in its terminal part, where a very extensive Peyer’s patch is found. The =cæcum= is about 10 to 12 inches (ca. 25 to 30 cm.) long, 2 inches (ca. 5 cm.) wide, and has a capacity of about a quart (ca. 1 liter). The =colon= is about 15 feet (ca. 4 to 5 m.) long. Its caliber is at first about the same as that of the cæcum, but diminishes to about the width of the small intestine.

FIG. 305.—LIVER OF SHEEP, VISCERAL SURFACE; HARDENED _in situ_.
]

The =liver= weighs about 20 to 25 ounces (ca. 550 to 700 gm.). It lies entirely to the right of the median plane. The parietal surface is related almost exclusively to the right part of the diaphragm. The visceral surface presents extensive reticular and abomasal impressions, and a small omasal impression internal to the portal fissure. The umbilical fissure is deep and partially divides the gland into two chief lobes. The caudate lobe is prismatic and blunt-pointed. The neck of the gall-bladder is long. The bile-duct joins the pancreatic duct to form a =common duct= (Ductus choledochus communis) which opens into the duodenum about one foot (ca. 30 cm.) from the pylorus.

The =pancreas= is arranged as in the ox. Its duct unites with the bile-duct.

The =spleen= (Fig. 301) is somewhat triangular, with the angles rounded off. It weighs about three or four ounces (ca. 100 grams). Its length is about five inches (ca. 12 to 13 cm.) and its greatest width about four inches (ca. 10 cm.). The parietal surface is convex and is related to the diaphragm, to which rather more than the anterior third is adherent. The visceral surface is concave and its anterior half is attached to the dorsal curvature of the rumen. The dorsal end or base is attached to the left crus of the diaphragm under the last two or three ribs. The hilus is at the posterior basal angle. The ventral end is narrower and thinner than the base; it is situated opposite the ninth and tenth ribs above their middles.

FIG. 306.—LIVER OF SHEEP, PARIETAL SURFACE; HARDENED _in situ_.
]

DIGESTIVE SYSTEM OF THE PIG

THE MOUTH

The =rima oris= is extensive, the angles of the mouth being situated far back. The =upper lip= is thick and short, and is blended with the snout; the =lower lip= is small and pointed. The labial glands are few and small.

The mucous membrane of the =cheeks= is smooth. The =buccal glands= are compactly arranged in two rows opposite the cheek teeth. The =parotid duct= opens opposite the fourth or fifth cheek tooth.

The =hard palate= is long and narrow; it is marked by a median furrow, on each side of which are twenty or more ridges. On its anterior part there is a triangular incisive papilla, at which the naso-palatine ducts open.

The =soft palate= is very thick. Its direction almost continues that of the hard palate, _i. e._, it is nearly horizontal. It extends to the middle of the oral surface of the epiglottis.[110] It has a median prolongation termed the =uvula=. The oral surface presents a median furrow, on either side of which is an oval raised area, marked by numerous crypts; these elevations are the =tonsils=. Tonsillar tissue also occurs in the lateral walls of the fauces.

FIG. 307.—TONGUE OF PIG.

_1_, Apex; _2_, dorsum; _3_, root; _a_, orifices of ducts of lingual
glands; _b_, papillæ of root; _c_, vallate papilla (not really so
distinct as in figure); _d_, foliate papilla; _e_, fungiform
papillæ; _f_, epiglottis (pulled back); _g_, median
glosso-epiglottic fold. (Ellenberger-Baum, Anat. _d_. Haustiere.)
]

The =tongue= is long and narrow and the apex is thin. Two or three vallate papillæ are present. The fungiform papillæ are small and are most numerous laterally. The filiform papillæ are soft and very small. On the root there are soft, long, pointed papillæ, directed backward. Foliate papillæ are also present.

There is a well-marked median glosso-epiglottic fold, on either side of which is a depression (Vallecula epiglottica). The frenum linguæ is double.

The =dental formula= of the pig is:

( 3 1 4 3 )
2 ( I - C - P - M - ) = 44
( 3 1 4 3 )

The formula for the temporary teeth is:

( 3 1 4 )
2 ( Di - Dc - Dp - ) = 32
( 3 1 4 )

The =upper incisors= are small; they are separated from each other by spaces, and from the canines by a larger interval. The first incisors are the largest, are convergent, and have no distinct neck. The second are narrower and somewhat smaller. The third (corner) incisors are much smaller, are flattened laterally, and have three small eminences on the crown.

The =lower incisors= are almost horizontal and are convergent and close together. The first and second are about equal in size, prismatic, and deeply implanted in the jaw. The labial surface is slightly convex, the lingual concave and marked near its extremity by a ridge. The third incisor is much smaller and has a short narrow crown and a distinct neck.

FIG. 308.—SKULL OF PIG ABOUT A YEAR AND A HALF OLD, SCULPTURED TO SHOW
THE EMBEDDED PARTS OF THE TEETH.

_I1–3_, Incisors; _C_, canines; _P1–4_, premolars; _M1–3_, molars.
]

The =canine teeth= or tusks of the male are greatly developed and project out of the mouth. The upper canine of the boar may be about three or four inches (ca. 8 to 10 cm.) long. The crown is conical and is curved somewhat backward and outward; the embedded part is curved and has a large pulp cavity.[111] The lower canine may reach a length of eight inches or more (ca. 20 cm.); the crown is prismatic and is curved backward and outward in front of the upper one, so that the friction between the two keeps a sharp edge on the lower tooth. In the sow they are much smaller.

FIG. 309.—SUPERFICIAL GLANDS OF HEAD OF PIG.

_a_, Parotid gland; _a′_, _a″_, cervical and submaxillary angles of
_a_; _b_, _c_, ventral and dorsal buccal glands; _d_, labial glands;
_e_, masseter muscle; _f_, _f′_, lymph glands; _g_, dotted line
indicating outline of submaxillary gland, which is concealed.
(Ellenberger-Baum, Anat. d. Haustiere.)
]

The average periods of =eruption= of the teeth are given in the subjoined table.

TOOTH│ ERUPTION │ CHANGE
│ │
I_{1}│2 to 4 weeks │12 months
I_{2}│upper 2 to 3 months│
│lower 1½ to 2 month│16 to 20 months
I_{3}│Before birth │8 to 10 months
C │Before birth │9 to 10 months
P_{1}│5 months │
─────┼───────────────────┼───────────────────
P_{2}│5 to 7 weeks │12 to 15 months
P_{3}│upper 4 to 8 days │ „
│lower 2 to 4 weeks.│
P_{4}│upper 4 to 8 days │ „
│lower 2 to 4 weeks │
─────┼───────────────────┼───────────────────
M_{1}│4 to 6 months │
M_{2}│8 to 12 months │
M_{3}│18 to 20 months │

The =cheek teeth= increase in size from before backward. They have (with certain exceptions noted below) complex tuberculate crowns; the term bunodont is applied to this condition, as distinguished from the selenodont structure in horses and cattle, in which there are prominent ridges of enamel. They are short-crowned teeth with a distinct neck and root. The first tooth in each jaw is small, simple, and appears only once; in the lower jaw it is near the canine, in the upper near the second cheek tooth. The next two teeth are larger, laterally compressed, and sectorial. The fourth tooth below is larger, but otherwise like the preceding ones, while the upper one is much wider and is tuberculate.

FIG. 310.—DISSECTION OF MOUTH AND PHARYNGEAL REGION OF PIG.

_1_, Hard palate; _2_, tongue showing distinctly fungiform papillæ;
_3_, foliate papilla; _4_, lymph nodules of soft palate; _5_,
stylo-glossus muscle, out of which a portion has been cut; _6_,
hyo-glossus; _7_, genio-glossus; _8_, genio-hyoideus; _9_,
mylo-hyoideus (reflected); _10_, stylo-hyoideus; _11_, great cornu
of hyoid bone; _12_, tensor palati; _13_, levator palati; _14_,
pterygo- et palato-pharyngeus; _15_, stylo-pharyngeus; _16_,
chondro-pharyngeus; _17_, sterno- et omo-hyoideus; _18_,
retropharyngeal lymph glands; _a_, bulla ossea; _b_, paramastoid
process. (Ellenberger-Baum, Anat. d. Haustiere.)
]

The =parotid gland= is large and triradiate. It extends very little on to the masseter muscle and its upper angle does not quite reach the base of the ear. It is pale in color, and is embedded in fat in animals in good condition. On its deep face are several large subparotid lymph glands, some of which are only partially covered by the parotid. The =duct= arises on the deep face, has a course similar to that of the ox, and perforates the cheek opposite the fourth or fifth upper cheek tooth. Small accessory glands (Glandulæ parotideæ accessoriæ) may be found along the course of the duct.

The =submaxillary gland= is small, reddish in color, and oval in outline; it is covered by the parotid. Its superficial face is convex, and is marked by rounded prominences. From its deep face a narrow process extends forward about two or three inches (ca. 5 to 7.5 cm.) beneath the mylo-hyoideus muscle along with the duct. The latter opens near the frenum linguæ, but there is no papilla.

FIG. 311.—SAGITTAL SECTION OF PHARYNGEAL REGION OF PIG, PARTLY
SCHEMATIC.

_1_, Palate bone; _2_, sphenoid bone; _2′_, sphenoidal sinus; _2″_
occipital bone; _3_, epiglottis; _4_, arytenoid cartilage; _5_,
thyroid cartilage; _6_, root of tongue; _7_, mouth cavity; _8_,
isthmus faucium; _9_, hard palate; _10_, septum nasi; _11_, ventral
muscles of head; _a_, soft palate; _a′_, free edge of _a_; _b_,
dorsal wall of pharynx; _c_, fornix of pharynx; _d_, cavity of
larynx; _e_, _g_, naso-pharynx; _f_, oro-pharynx; _h_, posterior
pillar of soft palate; _i_, dotted line indicating lateral boundary
between nasal cavity and pharynx; _k_, aditus laryngis; _l_,
entrance to œsophagus; _m_, Eustachian orifice; _n_, pharyngeal
recess; _o_, posterior naris. (After Ellenberger, in Leisering’s
Atlas.)
]

FIG. 312.—STOMACH OF PIG, PARIETAL SURFACE.

The organ contained a rather small amount of ingesta and hence is
somewhat contracted.
]

FIG. 313.—STOMACH OF PIG, VISCERAL SURFACE.

Organ was fixed _in situ_ and is somewhat contracted.
]

The =sublingual gland= has an arrangement similar to that of the ox. The posterior part (Glandula sublingualis grandicanalaris) is reddish-yellow in color, and is about two inches (ca. 5 cm.) long, and half an inch wide; its posterior end is in relation to the submaxillary gland and its duct. The anterior part is much larger, being two or three inches (ca. 5 to 7 cm.) long and about twice the width and thickness of the posterior part. All or most of the ducts from the posterior part unite to form the =ductus sublingualis major=, which opens near the ductus submaxillaris. Eight or ten =ductus sublinguales minores= convey the secretion from the anterior part through the floor of the mouth.

FIG. 314.—DIAGRAM OF ZONES OF MUCOUS MEMBRANE OF STOMACH OF PIG.
]

FIG. 315.—VISCERAL SURFACE OF STOMACH OF PIG, FROM WHICH THE SEROUS
COAT HAS BEEN REMOVED.
]

FIG. 316.—EVERTED STOMACH OF PIG, FROM WHICH THE MUCOUS MEMBRANE HAS
BEEN REMOVED.

_O_, Œsophagus; _D_, duodenum; _Di_, diverticulum; _a_, _a′_, _a″_,
_a‴_, longitudinal fibers; _b_, circular fibers; _c_, external
oblique fibers; _c′_, internal oblique fibers; _c″_, cardiac loop;
_d_, fibers which connect branches of cardiac loop; _f_, fold at
entrance to diverticulum; _p_, pyloric sphincter; _p′_, pyloric
prominence. (Ellenberger-Baum, Anat. d. Haustiere.)
]

THE PHARYNX

The =pharynx= presents in its posterior part a median cul-de-sac about an inch and a half (ca. 3 to 4 cm.) long, which is situated between the ventral straight muscles of the head and the origin of the œsophagus. Its lower margin is formed by the junction of the posterior pillars of the soft palate, which contain muscular tissue derived from the palatinus and palato-pharyngeus. The vault of the pharynx (Fornix pharyngis) is divided by a median fold of mucous membrane which is a direct continuation of the septum nasi. On either side of this is an infundibulum in which the Eustachian tube opens.

THE ŒSOPHAGUS

The =œsophagus= is short and nearly straight. It has (according to Rubeli) a potential caliber of nearly 3 inches (ca. 7 cm.) at either end, and about 1⁷⁄₁₀ inches (ca. 4.2 cm.) in its middle part.[112] The muscular coat, except near the cardia, is striated. There are mucous glands in the submucosa to about the middle of the tube.

FIG. 317.—ABDOMINAL VISCERA OF YOUNG PIG, VENTRAL ASPECT.

The stomach was very large in this subject.
]

FIG. 318.—DIAGRAM OF CÆCUM AND COLON OF PIG.

Coils of colon have been pulled apart somewhat.
]

FIG. 319.—SOLITARY NODULES FROM LARGE INTESTINE OF PIG.
(Ellenberger-Baum, Anat. d. Haustiere.)
]

FIG. 320.—ILEO-CÆCAL OPENING AND ADJACENT PART OF CÆCUM AND COLON OF
PIG.

_a_, Mucous membrane of colon; _b_, mucous membrane of cæcum; _c_,
Peyer’s patch; _d_, ileo-cæcal opening; _e_, end of ileum; _f_,
folds (frenula) of ileum. (After P. Schumann.)
]

THE STOMACH

The =stomach= is large and pyriform. Its average capacity is about 1½ to 2 gallons (ca. 5.7 to 8 liters). When full it extends backward to the last left intercostal space laterally and the umbilicus ventrally. The left portion is large and rounded, while the right portion (Pars pylorica) is small, and bends sharply upward to join the small intestine. The parietal surface is related to the liver, gall-bladder, and diaphragm. The visceral surface is related to the intestine, the mesentery, and the pancreas. The great curvature is related to the diaphragm, spleen, and abdominal floor. The pyloric end lies on the right lateral lobe of the liver. The left extremity presents a flattened conical blind pouch, the =diverticulum ventriculi=, the apex of which projects backward. The œsophagus joins the stomach very obliquely, almost in the median plane, and about three or four inches (ca. 8 to 10 cm.) below the twelfth thoracic vertebra. The cardiac opening is slit-like and is bounded above and to the left by a fold which contains a thickening of the internal oblique layer of the muscular coat. The opening into the diverticulum is situated above and a little to the left of the cardia; it is transversely oval, and is bounded (except externally) by a thick fold which contains spirally arranged muscular fibers. The mucous membrane may be divided into four regions. Over a quadrilateral area around the cardia (about one inch on the right and two or three inches on the left side of the orifice) it is œsophageal in character, and presents a number of folds. A sharp line of demarcation separates this from the rest of the mucous membrane, which is soft and glandular. The second or cardiac gland region is pale gray in color and thin (ca. 0.5 to 1 mm.); it extends about to the middle of the stomach. The third or fundus gland region is readily distinguished by its thickness (ca. 3 mm.) and its brownish-red mottled appearance.[113] The fourth or pyloric region is pale, thinner than the preceding, and presents a number of irregular folds. At the pylorus there is a remarkable ridge which projects from the wall of the lesser curvature and diminishes considerably the size of the orifice. It is about an inch and a half (ca. 3 to 4 cm.) long and nearly half an inch (ca. 1 cm.) high. Sometimes it is grooved; in other cases it has the form of a rounded eminence attached by a pedicle to the wall. Fibers from the circular muscular coat extend into it.

FIG. 321.—LIVER OF PIG, SOFT SPECIMEN SKETCHED WITH LOBES DRAWN APART.
]

THE INTESTINE

The =small intestine= is 50 to 65 feet (ca. 15 to 20 m.) long. The mesentery of about the first two feet (ca. 60 cm.) is two to two and a half inches (ca. 5 to 6 cm.) long; this part may be termed duodenum. The remainder (Jejuno-ileum) has a mesentery about six to eight inches (ca. 15 to 20 cm.) long, which is thick and contains a quantity of fat, and numerous large lymph glands at its root; the root is attached in the sublumbar region behind the stomach and blends here with the mesentery of the large intestine. The small intestine is arranged in close coils and lies mainly on the left side and floor of the abdomen, from the stomach to the pelvis; some coils, however, lie against the right flank. The opening of the =bile-duct= is about one or two inches (ca. 2.5 to 5 cm.) from the pylorus, and that of the =pancreatic duct= about four or five inches (ca. 10 to 15 cm.) beyond it. =Peyer’s patches= and =solitary glands= are numerous and very distinct; the patches are usually band-like and prominent; the solitary glands form projecting nodules marked by crypts.

FIG. 322.—LIVER OF PIG, VISCERAL SURFACE.

Photograph of specimen hardened _in situ_.
]

The =large intestine= is about 15 feet (ca. 4 to 5 meters) in length, and is for the most part much wider than the small intestine; it is connected by a mesentery with the dorsal abdominal wall between the kidneys. The =cæcum= is cylindrical, about 8 to 12 inches (ca. 20 to 30 cm.) long, and 3 to 4 inches (ca. 8 to 10 cm.) wide. It lies against the upper part of the right flank, its blind end reaching to within about two inches (ca. 5 cm.) of the pelvic inlet. The ileum joins the cæcum obliquely and projects somewhat into its lumen. The =colon= has at first about the same caliber as the cæcum, but becomes gradually smaller. Most of it is arranged in three close, double spiral coils in the mesentery, in relation chiefly to the right flank externally, and to the small intestine behind and to the left. On emerging from this spiral labyrinth, it passes forward to the stomach and pancreas and then turns backward; this terminal part is narrow, median in position, and closely attached by a short mesentery to the sublumbar region. The =rectum= is usually surrounded by a quantity of fat. The cæcum has three longitudinal muscular bands and three rows of sacculations, which are continued a short distance on the colon. The spiral colon has two bands and two series of sacculations, which, however, gradually disappear in the centrifugal part.

THE LIVER

FIG. 323.—LIVER OF PIG, PARIETAL SURFACE.

Photograph of specimen hardened _in situ_.
]