THE BASIS OF LIFE 17 



is " inverted." It is changed into a mixture of fruit-sugar and 

 levulose. The ferment invertin of the gastric juice and of 

 intestinal juice produces a similar effect ; and just as invertin 

 remains unchanged, so also the sulphuric acid is found in the 

 mixture unchanged in nature and in amount after an unlimited 

 inversion of cane-sugar. Great stress was formerly laid upon 

 the similarity between fermentation and catalysis. It has now 

 been shown that catalytic actions are not necessarily of the 

 same nature as fermentation, although the results and, as far as 

 is visible, the means are similar. For example, finely divided 

 platinum (or, better, palladium) causes an indefinite quantity 

 of oxygen and hydrogen to unite. The reaction comes within 

 the category of catalyses. But it is widely different from a 

 fermentation. The metal causes hydrogen to condense, and 

 actually absorbs it into its surface layer. In the liquid form 

 hydrogen cannot resist combination with oxygen. This may 

 be termed a " physical phenomenon," adopting the common 

 distinction between chemistry and physics. There is no reason 

 for thinking that fermentations can be explained in so simple 

 a way. They may, however, be grouped under the designa- 

 tion " catalyses." As the initial conditions and final results are 

 similar, it is inevitable that fermentations and catalyses should 

 obey the ^ame " laws " as to mass action, speed, effect of 

 accumulation of products of action, and the like ; but it does 

 not follow that invertin and sulphuric acid produce their 

 effects in the same way. Fermentations are instances of 

 catalysis, but all catalytic actions are not fermentations. 



So far from dwelling upon the resemblance between fermen- 

 tation and the catalysis of mineral chemistry, chemists now- 

 adays incline to regard fermentation as essentially a reaction 

 of life. It is very difficult, when attempting to present ideas 

 which are new to thought, to adapt, without ambiguity, existing 

 words. It would be absurd to talk of a substance removed 

 from yeast or bacteria or blood-corpuscles by a process which 

 involves cooling with liquid air, grinding with powdered glass, 

 solution in water, precipitation with absolute alcohol, and 

 re-solution in water, as alive. Yet, unlike any known mineral 

 product, it is easily killed. Ferments are not destroyed by 

 cold, but their activity is arrested. They are most active at 

 about the body temperature. Their activity is annihilated 



2 



