268 THE RABBIT 



(b) The hind-limbs are much longer than the fore-limbs. Each limb 

 is composed of a thigh, a leg, and a pes or foot. The foot 

 has four clawed digits. 



The Thoracic and Abdominal Viscera. 



Lay the rabbit on its back, and fasten it firmly to the dissecting-board by 

 putting large pins through the limbs. Make an incision through the skin, 

 beginning at the pelvis and continuing forwards along the mid-ventral line of 

 the body and neck to the region of the lower jaw. CarefuUj' free the skin from' 

 the underlying muscles. Note that a very thin sheet of muscle, the panniculus 

 caxnosus, lies immediately beneath the skin, and between it and the underlying 

 muscles is the panniculus adiposus, a layer of fat. In the female the mammary 

 glands may be seen, yellowish branching fat-like masses. 



Open the abdomen by making a median incision from the pelvic region to 

 the posterior end of the sternum, taking care not to injure the viscera. Cut 

 outwards, behind the ribs, and then pin out the flaps of muscle at each side. 

 Remove the ventral wall of the thorax {i.e., the sternum and lower portions of 

 the ribs) by cutting through the ribs (except the first pair) along each side. 

 Note the following organs in their position, and make a sketch of them : — 



(i) Thoracic Viscera. 



(a) The four-chambered heart, enveloped in the thin two-layered 



pericardium, and lying in the middle pf the thorax, in the 

 mediastinal space between the pleural sacs. 



(b) The thymus gland, in front of the heart, Mng over the arterial 



arches at their origin from the heart. 



(c) The lungs, two spongy organs occupying the sides of the thorax, 



and separated by the mediastinal space. The lungs are 

 attached at their roots only and are enclosed in pleural 

 sacs. 



(d) The lower portion of the trachea, which divides into the right 



and left bronchi which enter the lungs. 



(e) The diaphragm, separating the thorax from the abdomen. It 



is dome-shaped, and its margin is muscular. 

 (/) The oesophagus, lying underneath the trachea and extending 

 backwards through the thorax, under the backbone ; it passes 

 through the diaphragm to open into the stomach. 



(ii) Abdominal Viscera. 



(a) The liver, a large red solid organ attached to the diaphragm by 

 the suspensory ligament, a median vertical fold of peritoneum. 

 Its anterior surface is applied to the diaphragm and is convex ; 

 its posterior surface is concave and rests against the stomach. 

 The liver is divided into five lobes, viz. : — 



(1) The left central lobe, lying against the left half of the 



diaphragm. 



(2) The left lateral lobe, largest in size and partially 



