ALTERATIONS WHICH THE NUTRIMENT UNDERGOES. 555 



water are chiefly formed when , oxygen is present, and 

 beyond this only slight quantities of compounds which 

 are not so completely oxidised; where oxygen is ex- 

 cluded we still find a production of carbonic acid, which 

 is by no means insignificant in amount, but, nevertheless, 

 is much less than that produced by the respiratory pro- 

 cess (282 grammes of pears furnished, for example, in 

 5 months 1762 ccm. of carbonic acid) ; in addition, 

 alcohol, organic acids, and at times hydrogen, are 

 formed.* Only a very minute quantity of energy is set 

 free by the formation of these products from the more 

 complex molecules ; so that on the whole it is only for 

 a short time, and under otherwise favourable circum- 

 stances, that the requirements of the living cells as 

 regards energy can be supplied. 



Although this intra-molecular respiration, as has been 

 mentioned above, suffices for the complete supply of the 

 energy required in the case of the anaerobic fission 

 fungi, w T e have no facts with regard to the more intimate 

 processes in these cases, nor with regard to the products 

 formed. The tissue change of these organisms is more 

 easily analysed when they can at the same time excite 

 fermentation in the nutrient materials. In this case 

 they are under particularly favourable circumstances as 

 regards life, in that they have a substitute for the supply 

 of the necessary energy in the absence of oxygen. Under 

 these circumstances they are able to supplement the 

 decompositions which take place in their protoplasm in 

 such a way that a very large quantity of fermentescible 

 substances much more than the cells are usually able 

 to decompose in their interior is superficially broken 

 up with the liberation of energy ; and the latter is then 

 utilised by the living and growing cells to supply the 

 energy they require. At the same time, the substances 

 which undergo this decomposition cannot be completely 

 burned up; on the contrary, relatively complex pro- 

 ducts result, which differ much according to the fer- 



* Lechartier and Bellamy, Compt. rend., 1869, T. 69; 1872, T. 75; 

 1874, T. 79. Brefeld, Landicirthschaf. Jahrb., 1876. Miintz, Ann. 

 Chim. Phys., 1876. 



