HEART AND BLOOD VESSELS. 



11 



the ventricle ; the tube of exit, the artery ; and the pressure on the bulb is 

 effected by the contraction of the muscular walls of the heart, at more or 

 less regular intervals of, in the horse, about 40 in the minute. 



Starting at the left ventricle, we find that the blood contained in it, being 

 prevented by the valve of that side from entering the left auricle, is driven 

 by the contraction of the heart through the arteries, capillaries, and veins of 

 general circulation, into the right auricle, from which it escapes past the 



AiR C£U CAPILLARIES 



AIR CELL CAPlLLARieS 



PULMONARY ARTERIES 



.xz.. = -PULMONARr. VEINS 



/ilGHT AURICLE 



RIGHT VALVE 

 -i/GHT VENTRICLE 



VEIH5 OF GENERAL 

 CIRCULATION 



CAPILLARIES OE GENERAL 

 CIRCULATION 



- ARTERIES Of GENERAL 

 CIRCULATION 



CAPILLARIES OE GENERAL 

 CIRCULATION 



Fig. 3. — Diagram of the circulation of blood. 



valve of the right side, into the right ventricle. It is then driven by the 

 contraction of the right side of the heart, which occurs ."-imultaneously with 

 that of the left side, through the arteries, capillaries and veins of the pul- 

 monary circulation, until it flows into the left auricle, and finally past the left 

 valve into the left ventricle, where it completes its circuit, to be again pumped 

 round in the same VY^ay. According to the experiments of Hering and 



