258 Proceedings of Indiana Acade^ny of Science 



removed to a jar of cold water so as to cool the tubes at once. The 

 tubes, properly labelled, were then removed to be tested and were re- 

 placed by another series of tubes to be exposed to the next higher tem- 

 perature. Temperatures between 45° and 55°C. were thus tested. The 

 viability of the organisms in each series of heated tubes was tested by 

 means of loop transfers to tubes of slanted agar, and the suspensions 



Fig. 1. TheiTnal death-point apparatus. Large corl« float supports thei-momcter and 

 a number of small test tubes containing the bacterial suspensions. Temperature of water 

 bath adjusted by steam and cold water. 



were preserved so that additional transfers might be made from those 

 representing the critical temperatures. 



To summarize, the essential phases of this method are the use of 

 water suspensions in small test tubes, the use of a large, wooden con- 

 tainer for the water bath in which the temperature is raised by the ad- 

 dition of steam or hot water, the use of a cork float to support the tubes 

 and the thermometer, and the test for viability by making transfers to 

 agar slants. 



