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CHAPTER XXIT. 
THE ABDOMINAL AND PELVIC VISCERA. 
THE ABDOMEN AND ITS CONTENTS—PHYSIOLOGY OF DIGESTION—ABSORPTION—STRUO- 
TURE OF GLANDS AND PHYSIOLOGY OF SECRETION—DEPURATION AND ITS OFFICE 
IN THE ANIMAL ECONOMY—-ANATOMY OF THE SALIVARY GLANDS, PHARYNX, Q@SG- 
PHAGUS, AND STOMACH—THE INTESTINES—LIVER—SPLEEN—PA NCREAS—KIDNEYS— 
PELVIS—BLADDER—ORGANS OF GENERATION, MALE AND FEMALE. 
THE ABDOMEN AND ITS CONTENTS. 
LYING IMMEDIATELY BEHIND THE THORAX, from which they are separated 
only by the diaphragm, are the important organs of digestion, and the 
space in which they are closely packed is called the abdomen. This part 
is capable of being distended downwards and sideways to an enormous 
extent, or of contracting till the lower walls approach very closely to the 
upper. The anterior boundary, as before remarked, is the diaphragm, 
the plane of which moves considerably in active respiration, causing the 
flanks, or postero-lateral walls of the abdomen, to rise and fall, in a corre- 
sponding manner, and thus to indicate the extent of distress in an 
exhausted animal, or any pecuiiarity of breathing, as in “ broken wind,” 
or in the several inflammatory conditions of the lungs. Posterorly, the 
boundary is an open cne, being the anterior boundary of the pelvis, and 
corresponding with the brim cf that cavity. Superiorly are the crura of 
the diaphragm, the lumbar vertebra, and psoas and iliacus muscles ; and 
laterally, as well as inferiorly, the abdominal muscles, and cartilages of 
the false ribs. Although the abdominal muscles are capable of great 
dilatation, yet in the natural condition they maintain a gentle curve only 
from their pelvic to their costal attachments, and hence the depth and 
width of the back-ribs and pelvis are the measure of the ordinary 
capacity of the abdomen. Shallow and narrow back-ribs give a small 
abdominal cavity, and generally speaking a correspondingly weak con- 
dition of the digestive organs ; for though this rule is not invariable, yet 
it is one which may be held as a sufficient guide for practical purposes. 
Instances do occur of stout and hearty horses possessed of contracted 
middle pieces, but they are so rare as to be merely objects of curiosity. 
The small space which is devoted to the organs of digestion in the horse 
whose back ribs are shallow will be readily understood by reference to 
the annexed section, in which the enormous mass of intestines and the 
liver have been removed, leaving only the stomach and spleen. When 
the walls of the abdomen are distended laterally and downwards, as they 
always are in horses at grass, the capacity of the abdomen is at Icast 
doubled. 
THE CONTENTS OF THE ABDOMEN are the stomach, the liver, the pancreas, 
the spleen, the small and large intestines, the mesenteric glands and 
chyliferous ducts, and the kidneys, together with their vessels and nerves. 
Some of these organs are fixed closed to the spine, as the kidneys and 
pancreas ; but the others glide upon each other as they are alternately 
empty or full: and to facilitate this motion they are (like the lungs) 
invested with a serous coat, the peritoneum. They may be divided into 
the hollow organs, which form one continuous tube (the alimentary), and 
