68 PRINCIPLES OP VETERINARY SCIENCE 



The rapidity with which serous membranes absorb fluids makes 

 them very sensitive to infection. They never come in contact 

 with the external air. 



The peritoneum is the name given to the serous membrane 

 lining the abdominal and pelvic cavities. The most satisfactory 

 way to understand the general disposition of it is to think of 

 the cavity as empty and lined by a single layer of peritoneum 

 (Fig. 15). The organs may be regarded as beginning to develop 

 outside this membrane, and, as they enlarge, gradually push 



Fig. 15. — Diagrammatic cross-section of abdomen to show arrangement of 

 peritoneum when reduced to its simplest form. The external black line repre- 

 sents the body wall: 1, Organ (e.g., kidney) in contact with wall; 2, organ (e.g., 

 small intestine) at a distance from wall; 3, parietal peritoneum; 4, visceral peri- 

 toneum; 5, mesentery; 6, peritoneal cavity. (Si3son, Anatomy of Domestic 

 Animals.) 



into it and become enveloped by it. This causes folds of the 

 peritoneum to connect the organs with the wall or with each other. 

 The connecting folds are termed omenta, mesenteries, and liga- 

 ments. They contain fat in varying quantities, depending upon 

 the condition of the animal, and furnish a path for vessels and 

 nerves. The principal peritoneal folds are the great omentum, 

 the large lace-like membrane behind the stomach, and the great 

 mesentery, which suspends the small intestine from the roof of 

 the abdominal cavity. In the ox the great omentum is com- 

 monly known as the caul. 



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