304 THE ANATOMY OF THE HORSE. 



lar, tendinous, and elastic textures making up what is generally termed 

 the abdominal wall ; and superiorly it is bounded by the lumbar portion 

 of the spine clothed by the sublumbar muscles. 



Contents of the Cavity. — The cavity is occupied mainly by the gastro- 

 intestinal part of the alimentary tube, and its associated glands — the 

 liver and the pancreas. Besides these, it lodges the spleen and the 

 kidneys. In the female it contains the ovaries and the uterus (in part), 

 and in the male the vas deferftis passes through it. 



Divisions of the Cavity. — As a matter of convenience in describing 

 the position of its contained organs, the cavity is arbitrarily divided 

 into the following nine areas : — 



This subdivision is quite arbitrary, the boundaries between these areas 

 being certain imaginary planes. Thus, the three anterior regions are 

 separated from the three middle regions by a transverse vertical plane 

 passing through the lower end of the 15th rib, and the three middle 

 regions are separated from the three posterior regions by another trans- 

 verse vertical plane passing through the external angle of the ilium 

 (angle of the haunch). Again, each of these three regions — anterior, 

 middle, and posterior — is further subdivided into a central and two 

 lateral regions, this subdivision being effected by two vertical and 

 parallel longitudinal planes, each passing through the centre of Poupart's 

 ligament. 



Directions. — The intestines of the horse, owing to their unwieldy 

 size, and generally also to the weight of their contents, are extremely 

 inconvenient to dissect. From the following description and the 

 accompanying plates, the student should first learn how the intestinal 

 tube is divided. He should then, with as little disturbance of the 

 different intestines as possible, observe how they are disposed within 

 the abdominal cavity. 



The Intestines (Plates 41 and 42). The intestinal tube begins at 

 the pyloric orifice of the stomach, and it terminates on the surface 

 of the body, at the anus. It is primarily divided into small and 

 large intestines, and each of these is naturally or arbitrarily divided 

 into segments. 



The Small Intestine comprises the first portion of the tube, and in a 

 horse of medium size it measures about seventy-two feet in length. As 

 is expressed by its name, it is of smaller calibre than the large intestine. 

 Moreover, it is distinguished from nearly every part of the large intestine 

 by having a smooth and regular contour when distended. The first two 

 feet of the tube occupies a fixed position, and is termed the duodenum. 

 It received this name because in man its length is about equal to the 



