244 POPULAR SCIENCE MONTHLY. 



species that the optimum temperature for their development he as- 

 certained, and that this temperature he maintained. In this 

 respect we can distinguish three broafl groups. The first group in- 

 cludes those for which the optimum temperature is from 15-20° C. 

 The second group includes the parasitic forms, viz., those which grow 

 in the living body, and for which the optimum temperature is at 

 blood heat, viz., 37° C. We have a third group, for which the opti- 

 mum temperature lies as high as 50-55° C. On this account this 

 latter group has been termed thermophilic on account of its 

 growth at such abnormally high temperatures — temperatures which 

 are fatal to other forms of life. They have been the subject of per- 

 sonal investigation in conjunction with Dr. Blaxall. We found 

 that there existed- in nature an extensive group of such organisms to 

 which the term thermophilic bacteria was applicable. Their growth 

 and development occurred best at temperatures at which ordinary pro- 

 toplasm becomes inert or dies. The best growths were always ob- 

 tained at 55-65° C. Their wide distribution was of a striking nature. 

 They were found by us in river water and mud, in sewage and 

 also in a sample of sea water. They were present in the 

 digestive tract of man and animals, and in the surface and deep layers 

 of the soil, as well as in straw and in all samples of ensilage examined. 

 Their rapid growth at high temperatures was remarkable, the whole 

 surface of the culture medium being frequently overrun in from fifteen 

 to seventeen hours. The organisms examined by us (fourteen forms 

 in all) belonged to the group of the Bacilli. Some were motile, some 

 curdled milk and some liquefied gelatin in virtue of a proteolytic 

 enzyme. The majority possessed reducing powers upon nitrates 

 and decomposed proteid matter. In some instances cane sugar 

 was inverted and starch was diastased. These facts well illustrate 

 the full vitality of the organisms at these high temperatures, whilst 

 all the organisms isolated grew best at 55-65° C. A good growth in 

 a few cases occurred at 72° C. Evidence of growth was obtained even 

 at 74° C. They exhibited a remarkable and unique range of tempera- 

 ture, extending as far as 30° of the Centigrade scale. 



As a concluding instance of the activity of these organisms we 

 may cite their action upon cellulose. Cellulose is a substance that 

 is exceedingly difficult to decompose, and is, therefore, used in the 

 laboratory for filtering purposes in the form of Swedish filter paper, 

 on account of its resistance to the action of solvents. We allowed 

 these organisms to act on cellulose at 60° C. The result was that in 

 ten to fourteen days a complete disintegration of the cellulose had 

 taken place, probably in CO2 and marsh gas. The exact conditions that 

 may favor their growth, even if it be slow at subthermophilic tempera- 

 tures, are not yet known — they may possibly be of a chemical nature. 



