112 VICTOR E. SHELFORD. 



ration. In conclusion he states: "My experiments demonstrate 

 the enormous physiological and hygienic importance of ample 

 water evaporation in the tropics." 



Hill states that the increased blood count in mammals in high 

 altitudes and balloon ascensions is due to the transudation of 

 the lymph out of the peripheral vessels from which the sample 

 is drawn. Cronheim ('12) however insists that loss of water 

 through the lungs and through evaporation is the factor; no 

 doubt both are correct in a measure. Reduction of pressure 

 increases evaporation (Nothwang, '92). 



While from the standpoint of irritability little has been done 

 there is an excellent experimental basis for a statement of the 

 factors controlling the distribution of warm-blooded animals. 

 The importance of any factor on the distribution of animals is 

 its importance in the life of the animals. From the literature 

 cited and from other literature included in the bibliography it is 

 evident that in the case of mammals temperature data have little 

 significance unless the humidity is known. Neither of these 

 can be interpreted without a knowledge of the pressure, isolation, 

 and wind movement. The experimental foundation for the 

 consideration of all these factors was clearly laid down by 

 Reinhard ('69) and Rubner ('90). The best method of express- 

 ing them climatologically was stated by Shierbeck ('95) as the 

 amount of water evaporated. This does not mean that records 

 of the separate factors involved, namely, temperature, pressure 

 humidity, isolation, wind movement, etc., should not be made 

 but rather that the best expression of their combined action is 

 the rate of evaporation. 



The striking similarity of reaction and survival time to similar 

 rates of evaporation on the part of the animals regardless of 

 whether due to dryness, heat, or velocity speaks very strongly 

 for the measure of evaporation in connection with cold-blooded 

 animals. It is a noteworthy fact that the relation of warm- 

 blooded animals to climatic factors had been observed (Living- 

 stone, '58) and experimentally studied (Reinhard, '69; Rubner, '90) 

 before Merriam ('90, '94, '98) published his theory of tempera- 

 ture control (see Swain, '05; Craig, '08; Roosevelt, '10; Mathews, 

 '13). He made a most important contribution in his emphasis. 



