556 Ralph Hopkins and Gustav Mann, 



.with the unfatigued muscles of Table VI. The gastrocnemius of one 

 limb was curarixed to the extent of completely blocking nerve-im- 

 pulses at the motor- end plates. 



Results: 



1. In frogs heat-rigor occurs in voluntary muscles of the type 

 of the sartorius and gastrocnemius at a lower temperature than in 

 the slowly contracting voluntary tongue muscles, in tongue muscles 

 at a lower temperature than in the involuntary heart muscle, and in 

 heart muscles at a lower temperature than in the unstripecl bladder 

 and stomach muscles. 



2. A higher temperature is necessary for the coagulation of the 

 sartorius muscle of the northern frog than of the southern frog. This 

 difference is especially noticeable in the temperature necessary to 

 produce the second heat-contraction. 



3. Stomach and bladder muscles when gradually heated undergo 

 in the first instance a relaxation. The temperature necessary for the 

 production of heat rigor in these types of muscles is about 18 degrees 

 higher than that necessary to produce the first coagulation in sartorii 

 muscles, and is sligthly higher than the temperature which will 

 produce the second contraction in unfatigued sartorii muscles. 



4. Nicotine and atropine in unstriped muscles, and curare in 

 striped muscles apparently do not affect the temperature at which 

 the muscles coagulate. 



5. Fatigue, by the formation of acids, causes changes in muscles 

 of the type of the sartorius and gastrocnemius which makes these 

 muscles coagulate at a lower temperature. 



It is proposed to reverse the time order of the experiments 

 using northern frogs in the summer and southern frogs in the winter 

 with a view of determining the effect of hibernation on coagula- 

 bility. 



