
CHAPTER. xX 
THE LIMITS OF VITAL RESISTANCE TO HEAT: 
CONCLUSION 
po the commencement of the last chapter I had 
to refer to an exceptional group of organisms 
—the Conferve found in hot springs—which are 
capable of carrying on their very simple life-processes 
under conditions of temperature that have been 
found to be fatal to almost all other forms of life. 
And now I have to refer to an exceptional group of | 
Bacteria—the so-called ‘‘ Thermophilic Bacteria ”— 
which are capable of carrying on their simple life- 
processes at temperatures that would certainly prove 
fatal to many of their allies. These organisms have 
only been at all well known during the last ten years, 
the most extensive information concerning them 
being contained in two memoirs by Drs. Macfadyen 
and Blaxall. 
They say their researches have led them to the 
conclusion ‘that there is a widely distributed group 
of organisms in nature which find their optimum 
temperature of growth between 55 and 65 C.” 
Fourteen different forms have been studied and 
described by these investigators. They were all 
1 Journal of Pathology and Bacteriology, Nov. 1894, and Transac- 
tions of Jenner Institute of Preventive Medicine, second series, 1899. 
67 
