34r IOWA ACADEMY OF SCIENCES. 



morning, all of the frogs, thirty-seven in number, were found entirely 

 motionless and surrounded by ice, which, as the water had frozen had evi- 

 dently by the movements of the animals been kept in a mushy condition, in 

 which there was a very little water. This happened a second time, and in 

 neither case was there a single death. 



Two frogs were placed in a room where the temperature was one-half 

 degree above zero, one wrapped in a towel, the other put in a pasteboard 

 box filled with water, so that most of the expansion due to freezing would 

 be relieved by the bi'eaking of the box rather than exerting the whole strain 

 on the frog. These were left over night. In the morning the thermometer 

 marked sixteen degrees below zero. The one wrapped in a towel was 

 found frozen stiff and the other in a block of ice. Neither of these showed 

 signs of life on being thawed out. 



Four frogs were left in a cage for a week, during which time the tempera- 

 ture must have fallen at least twentj' degrees below zero. When examined 

 they were still enclosed in ice, and on being thawed out gave no signs of 

 life. 



Thus far no frogs have been frozen in ice without reducing the tempera- 

 ture much below zero, and under such circumstances it is barely possible 

 that life can be sustained. 



Last spring, while obtaining sets of developing frog eggs, a bottle con- 

 taining a number undergoing the second cleavage, was placed on the win- 

 dow sill where it remained several houi's. When examined the eggs were 

 found to be completely enclosed in ice, but when shaken they would quiver 

 in the albuminous mass surrounding them, showing that the albumen at 

 least was not frozen. Supposing the eggs were killed, the bottle was left 

 by the register, and when next examined the water was found to be much 

 warmer than my hand. After all this many of the eggs completed their 

 development and gave rise to active, evidently healthy, tadpoles. 



The amount of heat that adult frogs can stand is considerable, but no 

 appliances were at hand with which to experiment. The moist skin bars 

 them from standing such high temperatures as have been stood by men, but 

 it must be remembered that with men the temperature of the body varies 

 only a few degrees, although the surrounding temperature may vary a great 

 many degrees. With the frog the body varies through nearly as many 

 degrees of temperature as the surroundings in which it is placed. 



The prolonged vitality possessed by the muscles after destruction of the 

 central nervous system, or even after isolation from the body has led to the 

 use of frogs for some experiments in preference to most other animals. The 

 heart may be beating thirty-six or forty-eight hours after removal from the 

 body, and muscles will sometimes reopen to electric stimuli even after 

 putrefaction has set in. 



In all cases, in the live frog as a whole, or in the isolated tissues, vitalty 

 is quickly destroyed by a lack of moisture. A frog escaping from a cage to 

 a dry floor will generally die within twelve hours, and a muscle under 

 experiment must be moistened at intervals or it loses its irritability in a 

 very few minutes. 



The length of time that frogs can live without food has caused many 

 stories, such as finding live frogs in closed cavities in rocks. During the 

 summer frogs eat great quantities of food chiefly insects and worms, and 



