CHEMICAL BASIS "1 I Hi: ANIMAL 



tit'ii as indissolnhly connected with the vegetative LM'owth, multi- 

 plication, and metabolism of the yeast-cell. According to this view 

 sii^ar is tin- food-stuff out of whii-h the organism obtains the ma- 

 terial requisite for its metabolism and growth, the products of tin- 

 fermentation beinu' thus, as it wen-, the e\cn-tiunary residues of 

 tin- metabolised food. 1 A third vi-\v attributes tin- fermentative 

 uposition to the production l>y the organic -d t -nm-ntsof solu- 

 ble unorganised ! ix vines to whose activity tin- decomposition is 

 diii-. Th >-ceived its chief suii>urt DUD tin- discovery that 



a part at l-ast i>f the change which siujar undergoes in presence of 

 may be obtained by means of the soluble enzyme ' invi-rtin ' 

 which can readily be extracted from tin- dead cells. 2 But as yet 

 all efforts to obtain an i-nxyuie capable of carrying tin- decomposi- 

 tion beyond the initial stage of inversion have been fruit less. \ 

 cnling to von Nageli tin- living substance of the organised ct-11 is 

 to be regarded as being in continuous and rapid molecular vibra- 

 tion, ami the decomposition of the fermentable substance as tin- 

 result of the direct transference of these vibrations to this sub- 

 is by means of which its equilibrium is upset and it is split 

 up into simpler and therefore more stable products. 1 To discuss 

 the merits of these various theories and the experiments upon 

 which they are based is quite impossible within any reasonable 

 limits of brevity. We shall perhaps be not far wrong in consider- 

 ing that as regards the organised ferments the changes they effect 

 ;>e, iii their earlier stages, partly the outcome of the action of 

 some soluble en/vine, and partly the result of that cycle of meta- 

 bolic (chemical) processes which occur continuously in their proto- 

 plasm, in virtue of which they are sjMiken of as -living.' Simi- 

 larly in the higher animals we find a large number of Simpler 

 >n by means of isolal.le en/.ymes. by which un- 

 doubtedly the labours of the protoplasm in ierformiii'_: its own 



implicated activities an 1 materially lightened. l'>ut v. 

 still fare to face with nunilttrless decompositions which cam. 



reproduced outside tin- limits of living matter and which 



t be explained with reference to anything other than the 



activity of living matter 



The .jeiier.il ( oiiditious and factors which characterise the action 

 of tin- soluble ferments or enzymes have already been mentioned 



.; without making any suggestion as to the prohahl. 

 in which tln-v produce and .airy mi tin- decompositions to which 



tln-y -jive rise. Liebij - of the mode of action ot yeast, 



lince n left ! ; ind life of the cell entirely out ' 



w WM keenly attarked " n. ./. Cl>n* u I'h.irm. Bd. < MM 



: 8 lWnr in wply, A**. Ckim. l'ky> v. r I \\* . 



rtinir |-wfr f yemrt wo flmt dt.i nnif;iiit in I "47. I^rthHot 



-MI. a ml II - prepand it in t!i- I.. rin ( ; 



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