HEART-MUSCLE 



503 



(C) Again push the drum down so that the lever may write in a fresh 

 place just above the normal curve. With the pipet add a few centi- 

 meters of the Ringer's solution at 30. The heart soon beats much 

 more rapdily. Measure off the record and count the beats per minute. 

 (If the degree of heat be as high as 35, the ventricle ceases while the 

 auricle continues; a few degrees warmer, and the heart muscle dies in 

 heat-rigor.) Calculate the rate and percentage of change as before. 

 (See Fig. 153, page 286.) 



There is little that needs general explanation in these results. Almost 

 universally does protoplasm slow its action when cold and hasten it 

 when warmed to a degree somewhat below that of its coagulative death. 

 Poikilothermous animals show this better than homothermous animals 



FIG. 280 



Apparatus as set up by students to prove the action of electrolytic salines on the 

 frog's heart-muscle. 



could, for their tissues are adapted to these changes. The heart of a 

 frog buried in the mud at the bottom of a cold pool probably does not 

 beat fully all winter, but only hard enough to maintain a very sluggish 

 circulation. The same sort of cardiac acceleration obtains in persons 

 when they have a fever; that is, a relatively slight rise of body-tempera- 

 ture. In Daphnia the changes are much more marked than in the frog. 

 We saw the ameba hasten its streaming movements when it was warmed; 

 when in the water near the freezing-point it is apparently but a tiny drop 

 of almost motionless colloid. 



Expt. 67. The Importance of (Electrolytic f) Salines. Perfusion with 

 Ringer's Solution. (Apparatus: Heart-on cometer, Ringer's solution.) 



