Organs of the Animal Body : their Forms and Uses. 37 
For the purpose of getting an idea of the form and arrange- 
ment of the inside of the heart, portions must be cut from each 
side, as represented in Figures 24 and 25, which, with the 
short description, will enable the observer to get a better notion 
of the structures shown in the cavities which he has exposed 
than he would gain from a large volume of verbal description 
only. 
Fig. 24. — Bight side of Heart laid open. 
1, cavity of rigtt auricle ; 3, anterior vena cava opening into the right auricle; 4, posterior vena 
cava: a, right ventricle ; b, its cavity; e.f, valves between the light auricle and right ventricle te 
prevent return of blood when the ventricle contracis. 
Fig. 25. — Left Cavities of Heart laid open. 
1, cavity of left auricle ; 3, openings of two right pulmonary veins ; 5, left pulmonary veins (these 
vessels take the blood from the lungs into the left auricle); 8, left ventricle; 9, 9, its cavity; 
a, valve (mitral) between left ventricle and left auricle. 
Uses of the Heart and Vessels. — To trace the large vessels 
which are attached to the heart to their small branches can only 
