xm PHYLUM CHORDATA 313 



trunk, the tibia is pre-axia^ and the fibula post-axial : in the 

 natural position of the parts the pre-axial border is internal in all 

 three divisions of the limb. The femur is a stout bone consisting 

 of a shaft and two epiphyses. The proximal epiphysis develops a 

 rounded head which fits into the acetabulum ; near it on the 

 pre-axial side is a prominence, the lesser trochanter, and a nearly 

 obsolete prominence on the post-axial side represents the greater 

 trochanter. The distal extremity is pulley-shaped, with internal 

 and external prominences or condyles for articulation with the 

 tibia ; immediately above the external condyle is a prominence or 

 tuberosity for articulation with the fibula. The tibia is a stout, 

 curved bone, along the anterior (dorsal) edge of which runs a 

 longitudinal ridge, the cnemial ridge : the proximal extremity 

 presents two articular surfaces for the condyles of the femur. The 

 fibula is a slender bone, the proximal end articulating with the 

 external tuberosity of the femur, the distal with the tarsus. 



The tarsus (Fig. 977) comprises only 

 three bones in the adult, one large 

 proximal bone, the tibio-fibulare (tb. fb), 

 and two smaller distal (tars. dist). 

 Each digit consists of a metatarsal bone 

 and phalanges, the number of the latter 

 being respectively two, three, four, five, 

 and three. The first and second meta- 

 tarsals articulate with the tibial side of 

 the tibio-fibulare, the rest with the 



! ,FiG. 977. Tarsus of Lacerta agilis. 



distal tarsalS. fb. fibula ; tb. tibia ; tb. fb. tibio- 



Digestive System.-The upper and fi^f^X *f distal tarsals " 

 lower jaws, forming the boundary of 



the aperture of the mouth, are each provided with a single row of 

 small conical teeth, and there is a patch of similar teeth (palatine 

 teeth) on the palatine. On the floor of the mouth-cavity is the 

 tongue, a narrow elongated fleshy organ, bifid in front. 



The stomach (Fig. 978, M, Fig. 979, St) is a cylindrical organ 

 but little wider than the oesophagus, and with thick muscular walls. 

 At the point where the small intestine joins the large intestine or 

 rectum, the latter is produced into a short ccecum (Fig. 980, coec). 

 The liver (Ir) is divided into right and left lobes, and a gall-bladder 

 (Fig. 978, GB. ; Fig. 979, g.b ; Fig. 980, g.bl) lies at the lower 

 margin of the right lobe. The pancreas (pn) is situated in the loop 

 between the stomach and first part of the small intestine or duo- 

 denum (du). The stomach is attached to the body-wall by a fold of 

 peritoneum, the mesogaster, the small intestine by a fold termed the 

 mesentery, the rectum by a mesorectum. From the dorsal surface of 

 the liver to the stomach extends a thin fold, the gastro-Jiepatic omen- 

 turn ; and this is continued backwards as the duodeno-Tiepatic omentum, 

 connecting the liver with the first portion of the small intestine. 



