ABSORPTION AND ASSIMILATION OF NUTRIMENT. 545 



vital functions, and this is the more intelligible the Source of 

 more correct are our conclusions as to the absolute * 



relations of weight and energy in these minute beings ; anaerobes. 



or these organisms can take oxygen from certain nutrient 



materials and employ it for the oxidation of other com- 



plex substances. In the majority of cases the intra- 



molecular respiration does not permanently suffice to 



supply the necessary amount of energy for the bacteria, 



on the contrary they can only bear the loss of oxygen if 



a suitable substitute is present in its place. This sub- Substitution 



stitute is furnished by the fermentative process, in which the?imenta- 



a large amount of material present in the nutrient medium tive process. 



is broken up superficially, but nevertheless in such a 



manner that a quantity of energy is set free which is 



about equal to that obtained by the process of oxidation. 



Thus fermentation may take the place of the oxygen, 



and the respiration by means of oxygen and the fermen- 



tative activity may be looked on as of equal significance 



as regards their relation to the vital processes in the 



fungi. 



The little that is known as regards this peculiar mode 

 of tissue change and development of energy in the lower 

 fungi, may be put together in the following imperfect 

 description, in which the outlines of the picture which 

 will ultimately be constructed as the result of future 

 investigations are probably scarcely recognisable. 



2. The Absorption and Assimilation of the Nutrient 

 Materials by the Lower Fungi. 



As the penetration of the nutrient materials must take Absorption of 

 place in the case of the fungi, just as in that of every 

 vegetable cell, by means of diosmose through the cell 

 wall and the plasma, it is evident that only those sub- 

 stances can be taken up which are diffusible and present 

 in a watery solution ; where the fungi apparently feed on 

 solid materials, these substances are previously dissolved 

 . by the secretions of the organisms. In these preparatory 

 processes the chemical ferments produced by the fungi 

 take part ; for example, those which peptonise solid 



35 



