474 THE ANATOMY OF THE HORSE 



CHAPTER XXII 



THE ABDOMEN AND PELVIC VISCERA 



THE AnPOMEN AND ITS CONTl-.NTS— PIIYSIOLnGY OF DIGESTIOX— STRUCTURE OF GT.ANDS 

 AND rilYSIOLOaY OF SECRETION — DErURATIOX, AND ITS OFFICE IS THE ANIMAT, 

 EC0N0:MY — ANATOMY OF THE SAUVARY GLANDS, I'lrARYNX, O^SOPIIAfJUS, AND STOMACH 

 — THE INTESTINES— THE IJVKR— THE Sl'LEEN — THE TANOREAS— THE KIDNEYS— THK 

 PELVIS— THE BLADDER— THE OKCANS OF tJENERATION, MALE AND FEMALE. 



THE ABDOMEN AND ITS CONTENTS 



Lying immediately behind the thorax, from whicli tlu'v ure separated 

 only b}' the diaphragm, are tlic important organs of digestion, and tlie 

 space in whicli 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 postei'o-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 aii}^ peculiarity of breathing, as in "broken wind," or in the several inflam- 

 matory conditions of the lungs. Posteriorly, the boundary is an open one, 

 being the anterior boundary of the pelvis, and corresponding with the brim 

 of that cavit}'. Superiorly are the crura of the diaphragm, the lumbar 

 vertebra^ and psoas and iliacus muscles ; and laterally, as well as inferiorl}', 

 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 

 attachments, and hence the depth and width of the back ribs and pelvis 

 are the measure of the ordinary ca^iacity of the abdomen. Shallow and 

 narrow back ril)s give a small abdominal cavit}', and generall}' speaking a 

 correspondingly weak condition of the digestive organs ; for though this 

 rule is not invariable, yet it is one which maj' be held as a suflicient guide 

 for practical purposes. Instances do occur of stout and hearty liorses 

 possessed of contracted middle-pieces, but they are so rare as to be merel}' 

 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 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 ahvaj'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, 

 Ihe spleen, the small and large intestines, the mesenteric glands and 

 chyliforous ducts, and tlie kidne3's, together with their vessels and nerves. 

 Some of these organs are fixed close to the spine, as the kidneys and 



