36 PHYSIOLOGY AT THE FAKM. 



blind-gut is seen protruding from the colon, and encircled by 

 it as it extends to the right side. The small intestines are 

 not usually seen at first, but come into view when the caecum 

 is turned to the right side. The glistening appearance of all 

 the parts which are presented to view on opening the abdomen, 

 arises from the general investment of the contained organs 

 with the peritoneum or serous membrane of that cavity. The 

 peritoneum is the largest of the serous membranes in animals 

 resembling the horse; it forms, like other serous membranes, 

 a shut sac, resembling a double night-cap. The interior of 

 the sac throughout is the secreting surface ; the exterior of the 

 sac the surface of attachment, the former surface being every- 

 where free in the anatomical sense of that term, the latter sur- 

 face being everywhere joined to the face of the adjacent parts 

 by a thin connective layer of substance. The peritoneum is 

 the lining membrane of the abdominal cavity that is, one part 

 of the exterior surface of the shut sac, which it forms, makes 

 the lining of the cavity, while the remaining part of the 

 exterior surface adheres to and constitutes the outer coat or 

 covering of the several organs within the same cavity. The 

 part of the exterior surface of the peritoneal sac which consti- 

 tutes the outer covering of the several organs, is very intricate, 

 being thrown into numerous folds and processes, between the 

 laminae of which blood-vessels, nerves, and lymphatic vessels 

 pass, without, however, ever deviating from the type of a 

 double night-cap, to which it was likened above. The double 

 night-cap is simplicity itself compared to the intricacy of the 

 peritoneum. This point, however, still holds good throughout 

 all its intricacies, that the part of the night- cap which touches 

 the head corresponds to the surface of attachment in the 

 serous membrane, while the free glistening secreting surface 

 answers to the interior shut sac of the night-cap, to which 

 there is no access from without. Among the folds, consisting 



