196 HOMER E. CHENOWETH. 



ficient to raise the temperature 0.5 C. or more and thus produce 

 a gradient. The temperature of the different divisions of the 

 cage was recorded when a constant temperature seems to prevail. 

 Thermometers reading to one tenth of a degree were used. 



In Experiment 14, Charts I., the standard rate of flow, '27 

 liters per minute, was used, and the temperature in the differ- 

 ent thirds were 26.5, 24.2, and 23.2 respectively. The reac- 

 tions to the air of highest evaporation was similar to those of the 

 dry and rapidly moving air, and in this experiment the mouse 

 easily detected a difference of 3 C. In Experiment 15 the tem- 

 peratures were 25.2, 30.2, and 38.4 respectively while the rate 

 of flow was approximately 22 liters per minute. The dotted 

 line represents the reaction of the mouse after the ends were 

 reversed at the end of the experiment. The mouse was stimu- 

 lated at first in the hot air; activity was increased and it moved 

 back and forth in the cage for the first few minutes, after which 

 it selected the same air as before. 



(b) Resistance Experiments. The other experiments show that 

 the mice react to conditions of high evaporation. The following 

 were performed in order to determine how long they could with- 

 stand these unfavorable conditions. The standard rate of flow 

 used was the same as in previous experiments and the air was 

 dried and moistened as previously described. The mice were 

 put into large-mouthed bottles fitted with inlet and outlet tubes. 

 As soon as the air was turned on the temperature and relative 

 humidity were recorded. 



Three experiments were started at the same time. In one 

 bottle the mouse was treated with air of 15 per cent, relative 

 humidity and with an evaporating power of 1.3 c.c. All evapor- 

 ation readings are given for ten-minute readings. It died after 

 a 41 -hour treatment. In the second bottle the mouse was 

 treated with air of 95 per cent, relative humidity and the evapora- 

 tion was .3 c.c. The experiment was discontinued after 50 hours. 

 The mouse had acted normally throughout the experiment. In 

 the third bottle the mouse was treated with air that was warmed. 

 The humidity was 29 per cent, and the evaporation .7 c.c. Death 

 resulted after a 5O-hour treatment. In the warm air and the 

 dry air treatment the behavior of the mice was very similar. 



