A TURTLE 135 



the organs in the abdominal cavity are thus supported by mesen- 

 teries, which are folds of the peritoneum. 



In the posterior portion of the abdominal cavity are the uro- 

 genital organs. If the animal is a male, the spheroid testes, which 

 are usually of a yellow or reddish color, and the black epididymis, 

 which lies alongside and back of each one, will be seen. If a 

 female, the granular yellow ovaries and the tubular, convoluted 

 oviducts will be seen. The condition and extent of these organs, 

 however, are dependent upon the sexual condition of the animal. 

 The kidneys are dark-red organs which lie against the dorsal body 

 wall and will not yet be seen. At the hinder end of the abdominal 

 cavity is the large, bilobed urinary bladder, and back of it, beneath 

 the pelvis, is the cloaca, which leads to the anus. 



The large lungs are often visible in the abdominal cavity. They 

 may always be brought into view by blowing into the glottis 

 through a blowpipe. 



Exercise 6. Make an outline drawing of the ventral aspect of the 

 animal, showing the viscera as they lie in the body cavity. 



The Heart and its Vessels. Carefully dissect away what re- 

 mains of the ventral wall of the pericardium and the pectoral 

 muscles, so as to bring into view the forward portion of the heart 

 and the arteries springing from it. 



The heart is made up of the transversely elongated ventricle, the 

 two auricles, and the sinus venosus. The ventricle has thick, mus- 

 cular walls, and hence is usually not. so deep red as the thinner- 

 walled auricles and the sinus venosus. The auricles appear one 

 on each side of the forward end of the ventricle. The ventricle 

 is divided internally by a partial septum into two chambers which 

 communicate with each other. Springing from its anterior border 

 are the following arterial trunks: the left aorta, the innominate 

 artery, and the pulmonary artery. Directly in front of these in the 

 median line will be seen the small, round thyroid gland; the 

 trachea, or windpipe, may also be seen, and may be identified by 

 its cartilaginous rings. 



Of the arterial trunks, the one which appears on the animal's 

 right in the ventral aspect is the innominate artery. It branches 



