FERMENTS 23 



able to plants or animals, without themselves being used 

 up or suffering any permanent change (catalytic action). 

 They are regarded as albuminous substances : which are 

 formed from the protoplasm, and exhibit the above- 

 mentioned " catalytic " form of action. Poisons and 

 a too high temperature render them inactive. These 

 ferments may be precipitated from solutions, and 

 desiccated, but when redissolved, they continue to do 

 their work ; in fact, behave in a general way like 

 chemical substances. 



Enzymes may be classed according to their charac- 

 teristic action on starch, sugar, protein, fat, cellulose, 

 etc., and have generally a " hydrolising " effect ; z>., they 

 add the elements of water to the composition of the 

 substance acted upon, e.g., starch (C 6 H 10 O 5 ) becomes con- 

 verted into sugar (C 6 H 12 O 6 ). 



Enzymes are present in germinating seeds, and 

 perform the important function of converting the 

 starch contained in the seed into sugar, thus rendering 

 it available for the development of the young plant. 

 The same thing applies to tubers, bulbs, and vegetative 

 parts generally where food material is stored. 



In the animal body, ferments (enzymes) are secreted 

 by various glands along the alimentary canal, and are 

 largely responsible for changing food material into a 

 form in which it can be absorbed into the circulation, 

 as will be seen below. 



The process of digestion is much the same in 

 ruminants (e.g. cow) and non-ruminants (e.g. horse), after 

 the food has arrived at the so-called fourth "stomach" 

 in the case of the former, and the ordinary stomach in 

 the case of the latter ; hence the two will be dealt with 

 separately up to this point, and collectively after, 

 1 Strasburger. 



