156 



THE CIRCULATION 



22. A remarkable property of the tissue of the heart is its 

 intense vitality. For while it is more constantly active than 

 any other organ of the body, it is the last to part with its vital 

 energy. This is especially interesting in view of the fact that 

 after life is apparently extinguished, as from drowning, or 

 poisoning by chloroform, there yet lingers a spark of vitality 

 in the heart, which, by continued effort, may be fanned into a 

 flame so as to revivify the whole body. In cold-blooded ani- 

 mals, this irritability of the heart is especially remarkable. 



FIG. 38. DIAGRAM SHOWING THE POSITION FIG. 39. DIAGRAM SHOWING THE POSITION 

 OF THE VALVES OF THE HEART WHILE OF THE VALVES OF THE HEART DURING 

 THE WALLS ARE RELAXED THE , CONTRACTION OF THE VENTRICLES 



The heart of a turtle will pulsate, and the blood circulate for a 

 week after its head has been cut off ; and its heart will throb 

 regularly many hours after being cut out. The heart of a frog 

 or serpent, separated entirely from the body, will contract at 

 the end of ten or twelve hours ; that of an alligator has been 

 known to beat twenty-eight hours after the death of the 

 animal. 



23. Passage of the Blood through the Heart. Let us now 

 trace the course of the blood through the several cavities of 



22. Remarkable property of the tissue of the heart ? How shown ? How interesting ? 

 In mid blooded animals ? Heart of a turtle ? Of a frog ? Alligator? 

 2;J. Course of the blood through the heart ? Course of heart-currents ? 



