REACTIONS OF CERTAIN MOIST FOREST MAMMALS. 193 



CHART I. 



The chart shows the reactions of the white-footed %vood mouse to air of various 

 evaporative powers. The distance from right to left between the scales represents 

 the length of the cage. The vertical scles are time scales with minutes divided into 

 twelve second periods. The tracings represent the movements of the animals; 

 horizontal distance represents the distance lengthwise of the cage and vertical 

 distance represents time. The solid vertical lines separate the divisions corre- 

 sponding to the thirds of the cage. The number at the heads of these columns in the 

 experiments represent the evaporation in centimeters for the thirty-minute periods. 

 The relative humidity and temperature data is given at the bottom of the columns. 

 This chart shows a very marked avoidance of the air of high evaporation due to 

 dryness. The lowering of the threshold of stimulation is evident in Experiment 10, 

 as the period spent in the high evapoiation conditions is less each time until direct 

 orientation results. The mouse remained in this division of the cage forty-five 

 minutes after the experiment was closed during which time it slept. In Experiment 

 1 1 the filters and moisteners were renewed. The avoidance ot the air of high evapor- 

 ation is noted but this mouse reacted much more definitely which was probably 

 due to the dryer air and physiological state of the organism. The only time it left 

 the air of lowest evaporation it was forced out by the experimenter. The figures 

 at the top of the columns represent the evaporation in cubic centimeters during the 

 thirty-minute experimental periods and those at the bottom represent the relative 

 humidity. 



The chart shows the negative reaction of a mouse to air of high evaporation 

 due to increased air movement. In Experiment 12 the filters were removed from 

 the air supply and the moisteners were left in. The mouse oriented directly to the 

 air of highest evaporation, and the stimulation seems to be more of a mechanical 

 nature but undoubtedly the direct orientation is a reaction to the higher evaporation 

 due to the rapid air movement as well as the mechanical stimulus and loss of heat. 

 At the close of the experiment the two ends were reversed. The dotted line re- 

 presents the tracings ot the animal's movements. The same avoidance of the air 

 of high evaporation is noted but the mouse did not orient directly. It remained 

 in the unfavorable conditions foi ten minutes but became very restless after the 

 second minute and finally moved to the air of the same evaporation it had previously 

 selected. At the end of twenty-seven minutes it was forced out by the experimenter 

 but returned immediately to the air of lowest evaporation. In Experiment 13 the 

 moisteners were removed. When the mouse first encountered the rapidly moving 

 air it was stimulated and kept turning around in the cage and displayed other 

 random movements. Aftei icturning to the air of lowest evaporation and the less 

 rapid air movement the turnings were replaced by hesitation at the boundary of 

 the highest evaporation rates and shorter stays in the rapidly moving air. 



The chart shows the avoidance of high evapoiation due to increase of temper- 

 ature. In Experiment 14 a difference of 3.2 C. was noted. The standard rate of 

 flow, 27 liters pel minute, was used in this experiment. In Experiment 15 the oii- 

 entation to the higher temperature is more direct, and by comparing the two 

 experiments it is seen that temperature differences are easily detected by these mice. 

 The dotted line represents the tracings of the animal's movements when the ends 

 were reversed at the end of the experiment. The mouse ran around at random for 

 the first five minutes and then selected the air of the same evaporation it had 

 previously selected. 



