556 VITAL ACTIONS OF THE LOWEB, FUNGI. 



mentescible material, and are in part similar to those 

 which usually arise when the respiration is exclusively 

 intra-molecular. 



If We attem P fc to estimate quantitatively the tissue 

 change of the fungi in the manner usually employed in 

 the case of other organisms, viz., by placing on the one 

 side the quantity of material taken in, and on the other 

 side the amount which is destroyed, and also that 

 employed for building up new tissue, we soon find that 

 we are not as yet in a position to make any such 

 estimation. If fungi settle in a nutrient medium the 

 nutrient materials are consumed very quickly, the fungi 

 multiply rapidly, and a large portion of the nutrient 

 materials consumed is contained in the newly formed 

 colonies of cells which are distinctly visible to the naked 

 eye. Another portion has, however, been used up in 

 the respiration and in the destructive tissue change, 

 volatile products escaping and other excretory sub- 

 stances being dissolved in the nutrient medium. It 

 often happens that the elementary constitution of the 

 latter is completely altered, because the products of 

 the tissue change have set up changes which destroy 

 the nutrient qualities of the remainder of the nutrient 

 solution (formation of excess of acid or of an alkaline 

 reaction with precipitation of earthy phosphates, &c.). 

 Hence it is very difficult by analysis of the nutrient 

 substratum to estimate the relative results of assimila- 

 tion and of destruction, and we require more numerous 

 investigations before we can obtain an insight into 

 the quantitative relations of the tissue change of the 

 fungi. 



If we only pay attention to the process of assimilation, 

 and if we take into account the enormously rapid multi- 

 plication of the fungi, we can understand as the result of 

 this process alone the remarkably rapid consumption of 

 a nutrient medium (especially where fission fungi are con- 

 cerned). As above stated, we may assume that the 

 complete growth and the division of a bacterium into two 

 organisms occurs on an average within one hour ; a single 

 bacterium introduced into a nutrient solution furnishes 



