PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



EXPLANATION OF PLATE XV. 



Tracings obtained from an isolated heart nnder the influence of different tempera- 

 tures. The low, broad-topped curves on the upper part of tlie plate are j)roduced by 

 the lower temperatures and contrast Tery markedly with the long, sharp-pointed 

 ones lower down, which were produced by higher temperatures. 



