282 THE BIOLOGY OF THE FROG CHAP. 



from the lymph sacs. The lymph hearts are furnished with 

 a muscular coat composed of a network of bundles of striated 

 muscle fibers. 



The beating of the lymph hearts may readily be observed 

 in a recently killed frog. Often the pulsations of the pos- 

 terior lymph hearts may be seen beneath the skin, but they 

 are easily demonstrable in a very satisfactory manner by 

 removing the integument on each side of the end of the 

 urostyle. Their pulsations have no relation to those of the 

 heart, nor is there unison between the beats of the lymph 

 hearts on the two sides of the body. 



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