474 THE ANATOMY OF THE HORSE 



CHAPTER XXII 



TIIK ABDOMEN AND PELVIC VISCERA 



THE Ar.nOMEK AND ITS fOXTFNT.S— rnVSIOLOaY OF DIGESTIOX— STHUCTUr.K OF GLANDS 

 AND 1'IIYSIOI.OCIY OF SECRETION — DEPURATION, AND ITS OFFICE IN THE ANIMAL 

 ECONOMY — ANATOMY OF THE SALIVARY GLANDS, PIIARYNX, (ESOPHAGUS, AND STOMACH 

 — THE INTESTINES— THE LIVER — THE SPLEEN — THE PANCREAS — THE KIDNEYS — THE 

 PELVIS — THE BLADDER— THE ORCJANS OF GENERATION, MALE AND FEMALE. 



THE ABDOMEN AND ITS CONTENTS 



Lying immediately BEniND the thorax, from Avliich they are separated 

 only by tlie diaphragm, are the important organs of digestion, and tlie 

 space in wliicli 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 ^■ery 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 corresponding 

 manner, and thus to indicate the extent of distress in an exhausted animal, 

 or any peculiarity of breathing, as in " broken wind," or in the several inflam- 

 mator}' conditions of the lungs. Posteriorly, the boundary is an ojoen one, 

 being the anterior boundary of the pelvis, and cori^esponding with the brim 

 of that cavity. Superioi-ly are the crura of the diaphragm, the lumbar 

 vertebr.ie, 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 con- 

 dition they maintain a gentle curve only from their pelvic to their costal 

 attacliments, 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 cavit}'^, and generally speaking a 

 correspondingly weak condition 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 Avhich is devoted to the organs of 

 digestion in the horse whose back ribs are shallow will be readily under- 

 stood 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 down- 

 wards, as they alwaj's are in horses at grass, the capacity of the abdomen 

 is at least 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 close to the spine, as the kidneys and 



