Part 43

The abdominal cavity of the ox is very capacious, both absolutely and relatively, as compared with that of the horse. This is due to several factors. The lumbar portion of the spine is about one-fourth longer than that of the horse. The transverse diameter between the last ribs is greater. The costal attachment of the diaphragm is almost vertical in direction from the lower part of the ninth rib to the extreme upper part of the thirteenth; in fact, the attachment to the last rib is not constant. Thus the abdomen is increased at the expense of the thorax, and the last three or four ribs enter more largely into the formation of the abdominal wall than in the horse. The flank is also much more extensive. The ilia, on the other hand, do not extend forward beyond a transverse plane through the middle of the last lumbar vertebra. The epigastric and mesogastric regions would be separated by a plane through the lower end of the tenth pair of ribs, or through the last thoracic vertebra. The chief differential features in the arrangement of the peritoneum will be described with the viscera.

THE PELVIC CAVITY

The pelvic cavity is relatively long and narrow. The inlet is more oblique than that of the horse; it is elliptical in outline, and the transverse diameter is smaller than that of the horse. The anterior (pubic) part of the floor is about horizontal, but the posterior (ischial) part slopes upward and backward to a marked degree; this part is also deeply concave transversely. The roof is concave in both directions. The peritoneum extends backward as far as the first coccygeal vertebra, so that the retroperitoneal part of the cavity is short.

THE STOMACH

=General Arrangement.=—The stomach of the ox is very large, and occupies nearly three-fourths of the abdominal cavity. It fills all of the left half of the cavity (with the exception of the small space occupied by the spleen) and extends considerably over the median plane into the right half.

It is compound, being composed of four divisions, viz., =rumen=, =reticulum=, =omasum=, and =abomasum=.[107] The division is clearly indicated externally by furrows or constrictions. The first three divisions may be regarded as proventriculi or œsophageal sacculations, the fourth being the stomach proper (in the narrower sense of the term). The œsophagus opens into the stomach on a sort of dome formed by the rumen and reticulum, and is continued through the latter by the œsophageal groove. From the ventral end of the latter a groove traverses the ventral wall of the omasum, thus giving a direct path to the abomasum for finely divided or fluid food. The abomasum joins the small intestine.

=Capacity.=—The capacity of the stomach varies greatly, depending on the age and size of the animal. In cattle of medium size it holds 30 to 40 gallons, in large animals 40 to 60, in small 25 to 35. The relative sizes of the four parts vary with age. In the new-born calf the rumen and reticulum together are about half as large as the abomasum; in ten or twelve weeks this ratio is reversed. During this period the omasum appears to be contracted and functionless. At four months the rumen and reticulum together are about four times as large as the omasum and abomasum together. At about one and one-half years the omasum equals (or nearly so) the abomasum in capacity. The four divisions have now reached their definitive relative capacities, the rumen constituting about 80 per cent., the reticulum 5 per cent., the omasum 7 or 8 per cent., and the abomasum 8 or 7 per cent. of the total amount.

EXTERIOR AND RELATIONS

[Illustration:

FIG. 288.—PROJECTION OF VISCERA OF COW ON BODY-WALL, LEFT SIDE.

_Oes._, Œsophagus; _Ret._, reticulum; _b.s._, anterior blind sac; _b.s.′_, _b.s.″_, posterior blind sacs of rumen; _O_, ovary. The left kidney, concealed by the dorsal sac of the rumen, is indicated by dotted line. The median line of the diaphragm is dotted. ]

The =rumen= occupies almost all of the left half of the abdominal cavity, and extends considerably over the median plane ventrally and in its middle. It is somewhat compressed laterally, and may be described as having two surfaces, two curvatures or borders, and two extremities. The =parietal= (or left) =surface= (Facies parietalis) is convex and is related to the diaphragm, spleen, and the left wall of the abdomen. It extends from the lower part of the seventh intercostal space almost to the pelvis. The =visceral= (or right) =surface= (Facies visceralis) is somewhat irregular, and is related chiefly to the omasum and abomasum, the intestine, the liver, pancreas, kidneys, the uterus in the female, and the posterior aorta and vena cava. The =dorsal curvature= (Curvatura dorsalis) is convex, following the curve formed by the diaphragm and sublumbar muscles. It is firmly attached to the left portion of the crura of the diaphragm and the sublumbar muscles by peritoneum and connective tissue. The =ventral curvature= is also convex and lies on the floor of the abdomen. The surfaces are marked by the right and left =longitudinal furrows= (Sulci longitudinales), which indicate externally the division of the rumen into dorsal and ventral sacs.[108] The =reticular= (or anterior) =extremity= (Extremitas reticularis) is divided ventrally by a transverse groove (Sulcus ruminis cranialis) into two sacs. The dorsal sac is the longer of the two, and curves ventrally over the round, blind end of the ventral sac. The former only is continuous with the reticulum, a ventral groove (Sulcus rumino-reticularis) being the only external line of demarcation. Dorsally no natural separation exists, the rumen and reticulum together forming a dome-like vestibule (Atrium ventriculi) on which the œsophagus terminates. The =pelvic= (or posterior) =extremity= (Extremitas pelvina) extends nearly to the pubis, and is related to the intestine and bladder, and the uterus in the cow. It is divided into =dorsal= and =ventral blind sacs= (Saccus cæcus caudalis dorsalis, ventralis) by a deep transverse groove (Sulcus ruminis caudalis) in which the longitudinal furrows terminate. The blind sacs are marked off from the remainder of the rumen by the =dorsal= and =ventral coronary grooves= (Sulcus coronarius dorsalis, ventralis).

The left longitudinal groove (Sulcus longitudinalis sinister) begins at the anterior transverse groove, passes somewhat dorsally and backward and divides into two grooves. The ventral one is the chief groove and passes backward to terminate in the angle of union of the posterior blind sacs. The dorsal (accessory) groove curves dorsally and then backward to terminate in the dorsal coronary sulcus. On the right surface there are two longitudinal grooves. The dorsal one is the chief sulcus (Sulcus longitudinalis dexter). It extends in a curved direction (the convexity being dorsal) and is continuous with the left longitudinal groove by means of the grooves between the dorsal and ventral blind sacs at each end. The ventral groove (Sulcus accessorius) curves somewhat ventrally and backward to rejoin the chief sulcus between the posterior blind sacs.

The =reticulum= is the smallest of the four divisions in the ox. It is also the most anterior, and lies on the concave surface of the diaphragm, so that the median plane divides it into two nearly equal portions. It is somewhat pyriform, but much compressed from before backward. The =parietal= or =phrenic surface= (Facies diaphragmatica) is convex and lies against the diaphragm and liver.[109] The =ruminal= (or posterior) =surface= (Facies ruminalis) is flattened by the pressure of the other three compartments; it ends dorsally by joining the wall of the rumen, the concave line of junction forming, in the interior of the stomach, the lower margin of the large rumino-reticular orifice. The =omasal= (or right) =surface= is narrow and concave, and is connected with the omasum. The =dorsal curvature= by its left portion joins the rumen to form the atrium, and by its right portion touches the liver. The =ventral curvature= lies on the sternal portion of the diaphragm, opposite the sixth and seventh ribs. The =right extremity= forms a rounded cul-de-sac, which is in contact with the liver, omasum, and abomasum.

The =omasum= (Fig. 294) is ellipsoidal in form and somewhat compressed laterally. It is very clearly marked off from the other divisions. It is situated almost entirely to the right of the median plane, opposite the seventh to the eleventh ribs. The =parietal= (right) =surface= (Facies dextra) lies against the diaphragm, liver, and lateral wall of the abdomen. The contact with the latter extends over a small area only (ventral part of seventh to ninth intercostal spaces). The =visceral= (left) =surface= (Facies sinistra) is in contact with the rumen and reticulum. The =dorsal= (greater) =curvature= is convex, and is related to the diaphragm, liver, and vena cava. The =ventral= (lesser) =curvature= is concave, and rests on the abomasum chiefly, the junction with the latter appearing as a constriction near the middle of the curvature; at its anterior part there is a =neck= (Collum omasi) which is the connection with the reticulum.

The =abomasum= (Fig. 294) is an elongated pyriform or flask-shaped sac, which lies for the most part on the abdominal floor, to the right of the ventral sac of the rumen. Its narrow posterior part is strongly curved, the concavity being dorsal. The =parietal= (right) =surface= lies against the abdominal wall from the seventh to the twelfth intercostal space. The =visceral= (left) =surface= is related chiefly to the ventral sac of the rumen. The =dorsal= (lesser) =curvature= is concave, and is in contact with the omasum; the junction of the two sacs is indicated by a constriction about four or five inches (ca. 10 to 12 cm.) from the anterior extremity of the abomasum. The =ventral= (greater) =curvature= is convex, and rests on the abdominal wall from the xiphoid cartilage to the ventral part of the last (right) intercostal space. The =anterior extremity= forms a rounded blind sac which lies against the reticulum. The =posterior= (or pyloric) =extremity= is much smaller and bends upward and forward to join the duodenum. About six to eight inches (ca. 15 to 20 cm.) from the pylorus is a constriction which marks off the pyloric portion from the fundus.

The rumen is attached by peritoneum and connective tissue to the crura of the diaphragm and left psoas muscles, from the hiatus œsophageus backward to about the third or fourth lumbar vertebra.

The lesser omentum attaches the right face of the omasum and the pyloric portion of the abomasum to the visceral surface of the liver.

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.).

[Illustration:

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.

[Illustration:

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.

[Illustration:

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.

[Illustration:

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.