4 CLASSIFICATION OF FERMENTS. [BOOK II. 



the magnitude of the mass of the ferment engaged. These specific 

 actions of ferments lead to the breaking down of complex into 

 simpler molecules, the decomposition being necessarily associated 

 with the conversion of some potential into kinetic energy, which 

 usually appears as heat. 



' Unorganised! or as they have also been called, ' unformed ' 

 ferments differ, however, from the ' organised ' or 'formed ' ferments 

 in that, whilst they are the products of the activity of living proto- 

 plasm, they cease, after being formed, to have any necessary connec- 

 tion with organised forms, and have no power of reproduction or 

 increase. 



Certain enzymes exert their action unimpaired in the presence of 

 certain bodies which act as poisons to and kill the great majority of 

 organised ferments ; thus salicylic acid and thymol, in not too great 

 quantity, do not hinder peptic and tryptic digestion, but prevent the 

 putrefactive changes which are very apt to occur in the latter case, 

 and which depend upon the development of organised ferments. 

 Certain enzymes, however, as the diastase of malt, or as the diastatic 

 enzymes of saliva and pancreatic juice, are destroyed by salicylic 

 acid. 



Changes in As will be shewn in detail in the sequel, the secret- 

 secreting cells j n g ce }ig o f glands which produce enzymes exhibit 

 corresponding i i T/V- , 1-1 

 to variations marked differences or variations which correspond to 



in the func- different states of activity. In the case of the secreting 

 tionai activity cells of the pancreas, as was discovered by Heiden- 

 of organs. hain, the cells appear to produce and store up for a 



time a body, a so-called ' zymogen J from which an enzyme called 

 ' trypsin ' is set free ; similarly, as the researches of Ebstein and 

 Grlitzner, Langley and others have shewn, the secreting cells of 

 the gastric glands produce in the first instance an antecedent 

 of pepsin which we may term ' pepsin og en.' There is further 

 reason to believe that the rennet-ferment has a corresponding 

 zymogen. The progress of research will probably reveal the ex- 

 istence of zymogens in relation to other animal enzymes. 



Enzymes or Usually the glandular organs which produce the 



their, 'zymo- digestive juices contain stored up within them during 



gens 'usually Tv 8 V i i *% i 



present in the tne P eri ds in which they are actively secreting their 



secreting characteristic enzymes or their zymogens; these may 



structures be extracted by digesting the comminuted organ in 



which form water, weak spirit, chloroform -water or still better in 



b^extracte^ 7 gty cerm > which dissolves them nearly all, and furnishes 



therefrom. solutions which preserve their activity long unimpaired 1 . 



1 In reference to the solubility of enzymes and zymogens in glycerin, Mr Langley 

 has furnished me with the following note : 'I do not think it proved that ferments or 

 zymogens are soluble in pure strong glycerin. If they are -soluble it is extremely 

 slowly. If the oesophagus of a pig be dried and put in pure glycerin, in a well- 

 stoppered bottle, it does not give one-sixtieth of its ferment (counting zymogen as 



