COMMON FROG. 77 



large caeliaco-mesenteric artery before it unites with the right. The pulmonary 

 artery divides into the pulmonary vessel proper and the cutaneous artery. It 

 represents the fourth aortic arch of the Tadpole, the third disappearing. 



Each cava superior traced upwards breaks up successively into the external 

 jugular, the vena anonyma, and the cutanea magna, which receives the subclavian 

 vein. The cava inferior is formed by the union of the efferent -renal veins and 

 receives the veins of the genital glands, the fat bodies, and near the heart the 

 hepatic veins. The epigastric vein divides proximally into three branches, one for 

 each lobe of the liver, and a third which takes up the portal and splenic veins and 

 then enters the left liver lobe. Traced downwards, this vein receives first a cardiac 

 vein from the conus, secondly veins from the right and left abdominal parietes, 

 finally the veins of the allantoid bladder. It then divides into a right and left 

 branch traceable respectively to the right and left femoral veins. Each femoral 

 vein gives off also the reni-portal vein which passes to the outer side of the kidneys. 

 Into each reni-portal falls a dorso-lumbar vein, and in the female the oviducal veins. 

 Anastomoses exist between the allantoid, rectal and oviducal veins. 



The spleen is a reddish-brown body attached to the mesentery at the level of the 

 commencing rectum. A pair of lymphatic hearts opening into the subscapular veins 

 lie posteriorly to the outer ends of the transverse processes of the third vertebra. A 

 second pair lie one on either side the urostyle posteriorly, and opens into a vein which 

 falls into the communicating vein between the femoral and ischiadic veins. A large 

 lymphatic sac, cisterna lymphatica magna, lies at the back of the abdomen. Its ventral 

 wall, formed by the peritoneum, is pierced by microscopic apertures or stomata. 



There is an upper but no lower lip. On the roof of the mouth are (i) the minute 

 apertures of the intermaxillary glands, the homologues of the internasal glands of 

 the Urodela, immediately behind the fold of mucous membrane which protects the 

 praemaxiliary teeth; (2) the internal nares to the outer side of the vomers; (3) the 

 Eustachian tubes close to the articulation of the lower jaw. The broad flat tongue 

 is affixed to the symphysis of the mandible : its free end is bifid. In the male an 

 aperture on either side, close to the ramus of the lower jaw, leads to the croaking sac. 

 The teeth are conical, and restricted to the upper jaw and vomers. They consist 

 of enamel, dentine, and a bony base or pillar. New teeth are continually formed 

 during life to replace those that are worn or broken away. A short oesophagus 

 leads into a stomach which is at first dilated, then narrows to the pylorus, and lies 

 on the left side of the body. It is surrounded to a great extent by a lymph sac. The 

 duodenum is bent at a sharp angle with the stomach. The coils of the intestine 

 lie on the right side, and end in a short median dilated rectum which opens into 

 the cloaca dorsally to the aperture of the bifid allantoid bladder. The gall-bladder 

 lies in the notch between the median and right liver lobes. The pancreas is a 

 thin lobed gland lying between the stomach and duodenum ; its duct enters the 

 bile duct which opens on the dorsal wall of the duodenum. The aperture of the 

 larynx opens on the ventral wall of the oesophagus; it is protected by the two 

 arytenoid cartilages and a ring-like cricoid and leads to the two large oval lungs. 

 The lungs have much reticulated walls and are covered externally by peritoneum. 

 The thymus is a small gland lying close behind the angle of each jaw. The thy- 

 roid is paired, and each body lies in the angle between the two, i. e. the large and 

 small posterior horns of the hyoid, and adheres to the vena jugularis of its side. 



