MICHIGAN ACADEMY OF SCIENCE. 



95 



From this date the maxininiii teini)ei'ature seems to be about 

 ;]a-35° C, the optimum about 23-25 C. and the minimum around 

 11° C. 



THERMAL DEATH POINT. 



The apjiaiatus tor this experiment consisted (»t an iron vessel 

 tilled Willi water and agitated by a small motor-driven jiaddle. A 

 thermostat regulator attached to the gas bunier beneath kept the 

 water at the desired temperature and the tubes were ; uspended in 

 a wire basket. 



The temperature reading was made with a thermometer placed 

 in a test tube of the same size and thickness and containing the 

 same amount medium as those in which the spores were placed. 

 These tubes were 18 mm. in diameter and about .5 mm. in thickness. 



The temperature of the bath was held at the point desired from 

 o to 5 minutes before placing the culture in the water. When the 

 temperature was as desired the tube of melted agar was placed in 

 the bath for 3 minutes to bring it to the required temperature and 

 was then removed, quickly inoculated and placed again in the bath 

 for exactly 10 minutes, when it was taken out and plated; three 

 .><ets of test tubes were made with temperature ranging from 41°C. 

 to o8°(;. at intervals of 1°C. No growth appeared in jilates from 

 tubes heated above 50°(\ and the thermal death point appears to 

 be about 50°C. for 10 minutes. 



RELATION OF THE ORGANISM TO TEIMPER.VTURE AND HUMIDITY. 



These data were obtained through the kindness of Mr. H. J. 

 liuell, who conducted spraying experiments for the H. J. Heinz 

 Co., at Big Rapids, Mich., in 1914. 



The data on time of general infection was obtained from his 

 notes and the meteorological data from the United States Weather 

 Bureau reports. 



TABLE III. 



