554 Ralph Hopkins and Gustav Mann, 



actual contraction of the muscle. The kymograph was adjusted for 

 a speed of about two centimeters per minute, and time was marked 

 once eyerj ten seconds. A thermometer was suspended in the salt 

 solution, and, every rise of one degree was recorded by a signal 

 magnet. 



The vessel with the muscle suspended in salt solution was placed 

 in a larger vessel which was used as a water jacket to secure as 

 uniform a heating as possible. Corks were, used to prevent contact 

 between the bottoms of the two vessels. 



In some experiments one muscle only was used, but more often 

 two or three were heated at the same time in the same vessel for 

 purposes of comparison. 



Results: Table I shows the temperature at which contraction 

 occurred in a series of twelve sartorial muscles of the Louisiana bull- 

 frog. The column "commenced" indicates the temperature in degrees 

 centigrade at which the writing point departed from the abcissa line, 

 and "ends" indicates the temperature at which the writing point again 

 made a horizontal line. It will be noted that there were in most- 

 instances two contractions: one commencing about 35.7 degrees and 

 ending at 43.7 degrees and the other commencing about 53 degrees 

 and ending at 58.3 degrees. Rarely there was a third contraction at 

 a temperature above 50 degrees. "Time" indicates the number of 

 seconds which had elapsed from the commencement of the contraction 

 to its completion. As some of the muscles were heated more quickly 

 than others the time factor has varied. It would seem, within certain 

 limits, that the contractions continue until a temperature is reached 

 of about 43 degrees for the first contraction and about 58 degrees C. 

 for the second contraction, irrespective of the length of time taken 

 to attain these temperatures. 



Table II gives the results from five tongue muscles of the bull- 

 frog. In two instances the second contraction was inconsiderable, 

 and in one (frog 16) the muscle broke before a sufficient temperature 

 was attained to cause the second contraction. 



Table III. The heart muscle shows the greatest variation in 

 the coagulation temperature. In three instances (marked "no end" 



