0/ 



into a tiny cylinder which, witli the protruding cilia, 

 looked like a t'ox-tail. 



According to Pictet (1893) a ciliated epithelium from 

 the frog's mouth, frozen hard by exposure to a tempera- 

 ture of - 90°, resumed its beat after thawing, but expo- 

 sures to temperatures lower than - 90° killed the tissue. 



4. Muscular Tissue. In describing the investigations 

 on the muscles and on the heart we shall follow the chrono- 

 logical order. 



Kiihne (186-4) reported that frog muscles, frozen at 

 - 7° to - 10° for 3 hours, were irritable after thawing, and 

 that the irritability was observed to last for 6 hours at 15°. 



Jensen and Fischer (1909) demonstrated the funda- 

 mental fact, often confirmed by later investigators, that 

 some water can be congealed in the muscle without injur- 

 ing the latter, but that the solidification of more water 

 induces death. The gastrocnemius of Rana esculenta 

 was cooled to its lowest subcooling point (about -9°), 

 then it was left to freeze till past the end of the horizontal 

 portion of the freezing curve, or to various points in the 

 subsequent drop of the curve. The cooling process was 

 then interrupted and the reactivity of the muscle tested. 

 The temperature was indicated by a thermocouple. Cool- 

 ing to about - 1° and solidification of the greater part of 

 the free water produced no serious injury. With further 

 cooling, the reactivity and conductivity of the muscle de- 

 creased rapidly and disappeared at about - 3°. Since, in 

 this temperature interval, the more firmly bound water 

 began to freeze out, the death of the muscle, it is sug- 

 gested, might be correlated with this process. 



Brunow (1912) determined the death temperature of 

 the isolated frog's muscle in the following manner. He 

 drew the gastrocnemius of Rana fusca firmly into a nar- 

 row glass tube, centered this in a second wider tube, 

 letting an air space between them, and immersed the 

 whole into an ice-salt mixture, the temperature of which 

 was kept constant to within 1°. The temperature of the 

 muscle was determined bv means of a thermo-needle in- 



