Jl-NE. 191 J 



KNOWLEDGE. 



disease-producing bacteria : the present writer has 

 found that twenty-four hours' exposure of liver and 

 kidney press-juice to as low a temperature as minus 

 1 l^C does not in the least impair the subsequent capa- 

 bility of chemical reduction possessed by a tissue- 

 ferment provisionally known as "tissue-reductase.'" 



The fifth characteristic of ferment action is the 

 tendency of the ferments to be inhibited by the 

 accumulation of the products of their own activit\". 

 Thus alcohol rising to 14% puts an end to the 

 alcoholic fermentation in wine-making, the presence 

 of [leptones restrains pepsine. and similarK- in other 

 cases. The toxines of disease germs inhibit the 

 activity of the micro-organism ; \\hen this happens 

 in a living person, the person recovers. Of course 

 within the body an accumulation inhibitor\- to the 

 digestive enzymes does not occur, owing to the 

 constant absorption normally going on in the diges- 

 tive processes. 



.\n exceedingly interesting chapter in fermentation 

 is that dealing with the activators or the kinases as 

 they are called. Not all enzymes exist at all times 

 in an active state : certain enzymes are secreted in 

 an inactive state, and may remain inert until some 

 substance — which is not alwavs a ferment — has 

 reached them to activate them. These activators 

 may be dilute acids, sometimes they are other 

 ferments (kinasesl. Thus pepsine does not exist in 

 the active state in the cells of the gastric glands, but 

 in an inactive (zymogen) condition : this antecedent 

 state being known as pepsinogen. As soon, however, 

 as the hydrochloric acid of the gastric juice gains 

 access to the pepsinogen, it converts it rapidlj- into 

 the active pepsine. Thus the old puzzle, '" why does 

 the stomach not digest itself," is solved. The answer 

 is, the gastric glands do not contain the active form 

 of the ferment, but onl\- the inactive, or zymogen. .\ 

 \ery interesting case of ferment activation has been 

 discovered within the last few years. Freshly 

 secreted pancreatic juice does not of itself digest 

 albumins, neither does pure intestinal juice — the 

 siicciis entericiis — but if a very little succus be added 

 to the pancreatic juice, a most powerful digestive 

 action is developed, tr>psinogen has been acti\ated. 

 Now, since the addition of boiled succus entirely fails 

 to activate pancreatic juice, we seem justified in 

 believing in the existence of an enzyme in the 

 intestinal juice whose office it is to activate the pan- 

 creatic ; this kinase is called entero-kinase. 



Enzymes are not onlv exceedingl\- sensiti\e to 

 variations of temperature, but also to the chemical 

 reaction of the medium in which they find them- 

 selves. Thus ptyaline of the saliva can convert 

 starch to sugar only in a slighth" alkaline or neutral 

 medium, pepsine can act onl\- in an acid medium and 

 really well onlv in presence of hydrochloric acid from 

 • 2 "o to • 4 ",j, while the pancreatic enz\mes all need 

 frankly alkaline surroundings. Departures from the 

 normal acidity in the stomach constitute certain 

 forms of dyspepsia. 



Again, certain ferments only act properly in pre- 



sence of lime salts. Such are rennin, the milk-clotting, 

 and thrombase. the blood-clotting enzvme. The 

 discover\- of anti-ferments is one of the most 

 curious in this interesting subject. It explains 

 another old puzzle which was, '"Why are the 

 parasitic intestinal worms not digested b\' the 

 intestiiial juices of their hosts"? The answer 

 is that the worms have actually acquired the 

 power of producing a ferment which antagonises 

 the trypsine of the pancreatic juice: that is, an 

 anti-trypsine which effectually prevents the tryptic 

 enzyme exerting its solvent action on them. 

 This is a remarkable example of adaptation to 

 enx'ironmcnt. 



The last characteristic of ferments which may be 

 noticed is their specificity, individualitw or mutual 

 non-interchangeableness. Thus pepsine can act on 

 proteins, and on these alone ; it is quite powerless to 

 digest starch or jiure fat. Similarlv the starch- 

 dissolving enzymes are absolutely inert as regards 

 proteins or fats. 



But more than this as indicating a high specificit\-, 

 only those sugars containing six or nine atoms of 

 carbon are capable of alcoholic fermentation. Tlie 

 yeasts are perfectly non-affectable towards sugars 

 containing seven or eight atoms of carbon. These 

 latter sugars do not occur in Nature- tiu\' have 

 onl\- lately been synthetised by the chemist — so 

 that the yeasts and their ancestors have had no 

 experience of them. The \easts know nothing of 

 them : thev are unable to come into chemical 

 relationship with them. But bj- '" education " the 

 yeasts can be forced to become familiar with them, 

 to attack them — " which things are an allegor\-." 

 This curious specificity has been explained or rather 

 illustrated by the analogy of a lock-and-key. As 

 there is only one key which fits one Yale lock, so 

 there is only one enzyme which w ill break down or 

 dissolve one particular kind of substance. The 

 molecular configuration of the pepsine key will not 

 fit into the molecular structure of the starch or sugar 

 lock. 



In a certain sense, the discovery of ferments, or at 

 least the acceptance of the doctrine of enz\me-action, 

 has revolutionised biology. It is hardl\- too much 

 to say that life is SNiionymous with the power to 

 produce ferments. From the amcjeba in the stagnant 

 horse-pond up to the " noblest work of God," 

 enzvmes are essential to the exhibitions of vitality : 

 the ferments are omnipresent, and, in their own 

 sphere, omnipotent. 



It is curious, but true, that such exceedingly 

 different phenomena as the digesting of one's dinner, 

 the making of cheese, the manufacture of wine, the 

 disapi)earance of the dead, the colour of the delicate 

 corolla of the flower on the sun-lit hills and the 

 " uneffectual fire " of the gleam of the glow-worm 

 in the silence of the night, are alike due to these 

 hidden, mysterious, but none the less real, agents of 

 living matter, the soluble ferments. 



