REACTIONS OF CERTAIN MOIST FOREST MAMMALS. 199 



output increased in dry air. The following table will make this 

 clear. 



Increased irritability in the mice after a few invasions of the dry 

 air which caused them to turn back more quickly (See Graph i) 

 was probably due to increased CC>2 production. The differences 

 in water loss and CO2 given off is no doubt due to the varying 

 humidity and velocity of the air. He showed that the increased 

 water loss means an increased heat loss and therefore increased 

 metabolism if the body of the organism is to remain thermostatic; 

 that the ventilation of the lung is increased when the air tem- 

 perature is high; that CO* varies directly and not inversely as 

 the external temperature. These results show the importance 

 of humidity cannot be overestimated, for temperature data 

 without the known humidity is of no practical value. 



It is evident to naturalists that mammals select certain local 

 habitats for their chief places of abode and that their geographic 

 distribution is a function of the distribution of the conditions so 

 selected. In spite of many theories as to the factors controlling 

 distribution of mammals there are apparently no experiments 

 showing the factors to which they react in selecting their habitats. 

 The experiments performed show that the moist forest animals 

 studied avoid air of high evaporating power, due to dryness, 

 rapid movement or high temperature. The negative reactions 

 to air of high temperature which gives the same amount of 

 evaporation as dry air is no sharper than in the case of dry air 

 with no difference in temperature. 



The experiments indicate that in the case of the mammals 

 studied the rate of evaporation is more important than tem- 

 perature in determining their movements. Their resistance to 

 water withdrawal is far greater than that of any other animal in 

 the same community. 



IV. SUMMARY. 



i. The mice reacted to evaporation whether it was produced 

 by movement, dryness or heat (p. 192, 194-195). 



