498 



BIOLOGY OF THE MICRO-ORGANISMS. 



Pasteur's in- 



asto^e 008 



nutritive 



Fungi do not 



require "oim- 

 plex organic 



materials. 



stituents of their host and converting them into simple 

 chemical compounds. 



In correspondence with this view of the function and 

 the significance of the fungi, we must look for their 

 most important physiological peculiarities in the fact 

 that they ohtain their nutriment from complex organic 

 substances, and are unable to assimilate the carbon and 

 nitrogen from carbonic acid and ammonia. This charac- 

 teristic therefore formed the basis of former investi- 

 gations. 



Pasteur was the first who made exact experimental 

 investigations as to the biology of the fungi ; these ex- 

 periments led to results which differed in many respects 

 from the views which had been held up till that time. 

 Pasteur showed more especially that yeast and mould 

 fungi were in so far able to live in a similar manner to 

 the higher plants in that they could assimilate the 

 nitrogen from ammoniacal salts, and even from nitrates, 

 and thus, like the chlorophyllous plants, could build up 

 the complex albuminous materials of their body from 

 simple substances. It was also found that different 

 fungi showed great differences in their conditions of life ; 

 that one required oxygen and led to rapid oxidation, that 

 another could live without oxygen, and then often 

 caused extensive though superficial decomposition of the 

 nutrient material ; that only certain fungi could tolerate 

 an acid reaction and great concentration of the nutrient 

 medium ; that different organisms grew most luxuriantly 

 at very different temperatures ; that one preferred this, 

 and the other that kind of nutrient material, and that 

 they were not all equally capable of utilising the nitrogen 

 of ammonia, or of nitric acid ; that, lastly, even one and 

 the same organism behaved very differently as regards 

 their tissue change and energy under varying external 

 conditions. 



It is true that the former views as to the significance of 

 ^ e ^ un S^ ^ u na ^ure were not completely upset by these 

 results of experimental investigation. For it was still 

 certain that all the lower fungi were able to live on com- 

 plex chemical materials that, in fact, these materials 



