TESTS FOR PREGNANCY 



929 



into the left atrium. From the left atrium the blood passes into the left ven- 

 tricle and from thence out through the aortic root to supply heart tissues, 

 head region and systemic structures in general. On the other hand, the blood 

 from the superior vena cava flows through the right atrium to the right ven- 

 tricle, and from there it is propelled out into the proximal portion of the 

 pulmonary artery, and through the ductus arteriosus (Botalli) (left sixth aortal 

 arch) to the systemic aorta. The unaerated blood from the right ventricle 





Fig. 380. Care of young. (A) Egg capsule of Scyllium canicula (dogfish) contain- 

 ing developing egg fastened on seaweed by means of terminal tendrils. (Redrawn from 

 Kyle. 1926, The Biology of Fishes, Sidgwick and Jackson, Ltd.. London, after Varges. 

 (B) Male bowfin (Amia) guarding young. (Redrawn from Dean, 1896, Quart. J. Micros. 

 Sci. 38.) (C) Scarlet tanager feeding young. (Redrawn from photo by A. A. Allen, in 

 Pennsylvania Bird-Life, pub. by Pa. Game Commission, Harrisburg, Pa.) (D) Opos- 

 sum, suckling young. (E) Female hedgehog (Erinaceus eiiropetis) guarding young. (Re- 

 drawn from Figuier. 1870, Mammalia. D. Appleton and Co., New York.) 



