98 



SANITARY ENTOMOLOGY 



chart paper and a humidity scale from zero to one hundred per cent 

 saturation horizontally. 



If we picture our reactions or those of the creature being studied 

 on such a chart (see figs. 8, 9), we will better understand the subject. 

 In the lower part of the chart we will locate certain temperatures which 

 always cause death from cold. These may be known as ABSOLUTE 

 FATAL TEMPERATURES. 



Now a common failing in the past has been to assume that humidity 

 had nothing to do witli the effect of temperature on life. It does have 

 a very decided bearing. A creature which can stand a certain degree 



M HrPCfHfriCAL CHART SHOWING TH[ ZO^fS Of LIFE RfACTIONS TO 

 TCMPffiMORE m niKim humidity, OlfftRlNC W EACH SPEC/ES. 



Fig. 8 



of cold at a given humidity may be absolutely unable to stand that same 

 temperature at another degree of saturation or relative humidity. 



Our absolutely fatal temperatures tlierefore will form some sort of 

 a zone on our chart and this zone will probably be bounded by a curve. 

 We call tlie temperatures below this curve the LOWER ZONE OF 

 FATAL TEMPERATURES. Death caused by cold is called RHIGO- 

 PLEGIA. 



Slightly above these absolutely fatal temperatures will be a zone of 

 temperatures which might cause death if experienced sufficiently long, 

 but which at least cause a complete suspension of all activity. And 

 still higher will be temperatures which also cause suspension of activity, 

 but which do not cause death even when experienced for very long pe- 



