MAMMALS 



15 



The heart of mammals (Fig. 8) is four-chambered, a 

 feature easily seen if a section is made (Fig. 9). It is the 



f g ^'^ s 



Fig. 8. — Heart of the Dugong, a 

 Four-chambered Heart, the 

 Parts being more separated 

 than in the higher animals. 



E, right ventricle ; L, left ventricle ; 

 D, right auricle; F, pulmonary ar- 

 tery ; K, left auricle ; A, aorta. 



Fig. 9. —Theoretical Section of 

 THE Human Heart. 



a, right ventricle; b, inferior vena cava; 

 c, tricuspid valve ; d, right auricle ; 

 e, pulmonary veins ; f, superior vena 

 cava ; g, pulmonary arteries ; h, 

 aorta; -^, left auricle ; /, mitral valve; 

 m, left ventricle ; n^ septum. 



pump which forces blood through the body to the lungs, 

 where it is aerated. 

 The blood contains two 

 kinds of corpuscles 

 (Fig. 10), red and 

 white. The red cor- 

 puscles differ so much 

 in different animals 

 that experts can read- 

 ily distinguish animals 

 by them. No more 

 attractive sight under 

 the microscope can be ^'''- ^^--Red blood corpuscles of man. 



, , , , rt, shows circular contour ; b, a biconcave sec- 



imagmed than the web tion ; c, a group in chains. 



