ANATOMY OF THE FROG 41 



tissue. The left lobe is much the largest, and is divided into 

 two secondary lobes by a deep fissure extending forwards from 

 its hinder margin. If the lobes of the liver be turned forwards, 

 a round or oval vesicle, the gall-bladder, may be seen in the 

 deep fissure between the right and left lobes. It has thin 

 walls, and is generally full of a green fluid, the bile, which 

 imparts its colour to the whole bladder. The gall-bladder 

 receives bile from the liver by means of three ducts, which pass 

 from the lobes of the liver, unite together, and enter the gall- 

 bladder at its upper end as a single vessel, the cystic duct. 

 The bile is carried from the liver and gall-bladder to the 

 duodenum by a single duct, the bile duct, or ductus choledochus, 

 which is formed by the union of three vessels arising from the 

 cystic duct, and is joined, at some distance from its origin, by 

 several vessels from the middle lobe of the liver. 



The bile duct, in its passage towards the duodenum, traverses 

 the whitish lobular gland which we have already noticed lying 

 between the stomach and duodenum. This is the pancreas, a 

 gland which secretes a solvent fluid, the pancreatic juice. The 

 ducts of the pancreas join the bile duct about the middle of 

 its course, and the common biliary and pancreatic duct opens 

 into the duodenum on its dorsal surface about half-an-inch 

 beyond the pylorus. 



The liver and pancreas are the two glands which discharge 

 their secretions into the alimentary canal by ducts. Both of 

 them were formed, in the course of development, as outgrowths 

 of the embryonic gut. The stomach and intestine are also 

 glandular, their lining membrane being thrown into longitudinal 

 folds for increase of surface ; and the walls of these folds are 

 studded with innumerable minute orifices, the openings of 

 microscopically small gastric and intestinal glands, which dis- 

 charge their secretions into the cavity of the gut. These 

 glands are of very simple construction, being nothing more 

 than finger-shaped depressions lined by the mucous membrane 

 lining the gut. We shall study their characters more closely 

 hereafter. 



In studying the buccal cavity of the frog we noticed, on the 

 floor of its hinder end, a slit-like aperture, the glottis. This 

 opens into a short, wide tube, whose walls are strengthened by 

 a rather complex set of cartilages. This tube is the larynx. 

 The cartilages are five in number: a single curiously shaped 



