10 PHYSIOLOGICAL CHEMISTRY. 



ration of pure enzymes. The continued heating of their solutions 

 above + 80 C. generally destroys most of the enzymes. In the 

 dry state, however, certain enzymes may be heated to 100 or indeed 

 to 150-160 C. without losing their power. The enzymes are pre- 

 cipitated from their solutions by alcohol. 



We have no characteristic reactions for the enzymes in general, 

 and each enzyme is characterized by its specific action and by the 

 conditions under which it develops. But it must be stated that, 

 however the different enzymes may vary in action, they all seem to 

 have this in common, that by their presence an impulse is given to 

 split more complicated combinations into simpler ones, whereby the 

 atoms arrange themselves from an unstable equilibrium into a more 

 stable one, chemical tension is transformed into living force, and 

 new products are formed with lower heat of combustion than the 

 original substance. The presence of water seems to be a necessary 

 factor in the perfection of such decompositions, and the chemical 

 process seems to consist in the taking up of the elements of water. 

 The manner in which these enzymes work is still enveloped in 

 darkness, but their action may be considered as very closely related 

 to the so-called catalytic or contact action. 



As above stated, the enzymes are of great importance for the 

 chemical processes going on in the digestive tract, but we have to 

 add that the results of their action is greatly complicated by pro- 

 cesses of putrefaction which take place in the intestines at the same 

 time, and which are caused by micro-organisms. Micro-organisms 

 are physiological constituents of the contents of the intestinal canal, 

 and it is therefore to be supposed that also lower organisms or their 

 germs are to be encountered in the animal tissues and fluids gen- 

 erally, under normal conditions. The question is still unsettled as 

 to how far this is the case. But as yet no positive or decisive proof 

 for the justification of such a statement has been furnished. The 

 lower organisms, on the contrary, when they enter into the animal 

 fluids or tissues and develop and increase, are of the greatest patho- 

 logical importance, and modern bacteriology, founded by KOCH 

 and PASTEUE, in relation to the doctrine of infectious diseases, 

 gives efficient testimony to these facts. 



Putrefaction caused within the animal fluids and tissues by the 

 lower organisms may produce, among others, combinations of a 



