472 ZOOLOGY. 



1st, the sinus venosus ; 2d, both auricles ; 3d, the ventricle ; 

 4th, the truncus. 



In front of and below the heart may be seen the trachea, 

 easily recognized by the hard rings of cartilage, and having 

 the larynx just in front of the aortic arches and giving off 

 two branches posteriorly, the bronchi, which run directly to 

 the lungs. The trachea overlies the oesophagus, which ter- 

 minates in the stomach (St). On either side of the trachea 

 lies a thyroid gland (th). 



The liver (Li) is a large brown mass, composed of two 

 lobes, of which the left is the larger, and subdivided into 

 two. Between the two lobes lies a small greenish sac, the 

 gall-bladder (b). The liver receives a large vein (pv) from 

 the kidneys ; this is the portal vein, which distributes to the 

 liver the blood which has already once passed through the 

 capillaries of the other abdominal viscera. The hepatic vein 

 takes the blood from the liver directly to the heart. 



The stomach (St), when in situ, lies on the left side of the 

 abdominal cavity, its oesophageal end being the largest ; it 

 leads directly into the intestine, which is of uniform width 

 throughout, but terminates in the dilated rectum (R), which 

 in its turn opens into the cloaca. To the ventral surface of 

 the cloaca is appended the bladder (B). Imbedded in the 

 mesentery near the commencement of the intestine is a pale 

 compact mass, the pancreas, not represented in the figure, 

 and a little farther from the stomach a small round dark 

 body, the spleen (Sp). 



The kidneys (Kl) are two elongated deep red bodies, upon 

 which lie a number of yellow spots, the adrenal gland*. 

 The renal ducts arise from the outer and anterior portion of 

 the kidneys and then run backwards as two white convoluted 

 canals (vd), at first very narrow, then widening, and end- 

 ing with a dilatation immediately before they open into the 

 cloaca. These ducts serve at once as ureters and vasa defer- 

 entia. In front of the kidneys lie a pair of oval yellow 

 bodies, the testes (Te). The female has both ureter and 

 oviduct. The ovary varies greatly in size and appearance 

 according to its condition. The oviduct is a very long con- 

 voluted tube running from the pericardium backwards to 



