THE FROG. 181 



of this girdle. Continue the cut forward to the base of the 

 tongue. Stretch the fore legs out at right angles to the 

 body, and pin them so. Turn back the edges of the last 

 incision, and fully expose the organs of the body cavity. 



Internal Features. Perhaps the most conspicuous of 

 the internal organs is the large, mottled reddish liver, 

 which consists of a large double lobe on the right side 

 of the body, and of a smaller single lobe on the left side. 

 Immediately in front of the liver is the heart, inclosed in 

 a thin, transparent sac, the pericardium. If the heart is 

 still beating, the arterial system should be injected. 1 



Pinch up the pericardium with forceps, and cut it away 

 with sharp scissors. Cut away also its attachments to 

 the body wall, taking great care not to cut any blood 

 vessels or other organs. 



Pass a pipette or blowpipe through the mouth, into 

 the trachea, and inflate the lungs to' see their size and 

 position. 



I. Digestive Organs. Pass a long probe through the 

 mouth and pharynx into the esophagus, and thence back- 

 ward into the long, white stomach, which lies just behind, 

 or partly concealed by, the liver. From the posterior end 

 of the stomach trace the intestine. It turns forward, 

 downward, backward, then forms a spire on the right side 

 of the body, and then, returning to the median line, 

 enters an expanded terminal portion, the cloaca. Ducts 

 from the reproductive and renal organs also enter this 

 chamber. Observe the mesentery with which the intes- 

 tine is invested, and through which its blood vessels pass. 

 The position of the liver has been noticed : find the 

 greenish gall bladder attached to one of its lobes, and find 

 a duct leading from the gall bladder to the intestine. 

 This duct will usually be made more evident by squeezing 



1 For the method, see Appendix, p. 285. 



