THE PROBLEMS OF THERAPEUTICS 173 



to that of a man who opens the blade of a knife and renders an 

 instrument previously inactive very active indeed. If trypsine were 

 absorbed into the blood unchanged it might digest the tissues them- 

 selves and it must be rendered again inactive. This seems to be 

 effected by certain substances present in the blood which have a 

 so-called "anti" action upon the ferments and render them again 

 inactive. But though the digestive ferments might do harm if pre- 

 sent in the blood in an active form and in large quantity, yet it is prob- 

 able that all the cells of the body digest the food which is brought 

 to them by the blood and tissue juices and break up this food for 

 their own use by ferments which they contain themselves. Thirty 

 years ago I advanced this view and supported it by the fact that I 

 was able to extract from muscle by glycerine a substance which 

 decomposed sugar. This observation received but very little atten- 

 tion at the time, but recently German literature is full of papers 

 which support my views and confirm my results, although their 

 writers apparently are ignorant of my work. Fifteen years ago, 

 along with Dr. Macfadyen, I showed that bacteria not only excrete 

 ferments by which the soil in which they are growing is digested, 

 but that they are able to modify these ferments in accordance with 

 the soil so as to digest either proteid matter or sugar. Curiously 

 enough, within the last few years the pancreas in animals has been 

 shown by Professor Pawlow to have similar powers. 



No individual microbe has received so much attention as the yeast 

 plant and no poison which is formed by any of them has done so much 

 harm as the toxin or poisonous substance produced by yeast, for this 

 toxin is alcohol, whose poisonous action has given rise to the term 

 intoxication. The yeast-plant, when grown in sugar, excretes into it 

 a ferment, invertase, which splits up ordinary cane-sugar or sacch- 

 arose into two other sugars, dextrose and levulose. The yeast-plant 

 may be separated from the solution of sugar by filtration, but the 

 ferment which is already excreted will remain in the filtrate and may 

 still continue to act on the sugar, just as pepsin may dissolve a piece 

 of meat in a jar although the pig which produced it is dead and gone. 

 But no alcohol will be formed by this excreted ferment. Alcohol is 

 produced by something contained within the body of the yeast itself 

 and its production was formerly supposed to be due to so-called 

 vital action. It has now, I think, been proved that alcohol is pro- 

 duced by the action of a ferment which is contained within the body 

 of the yeast-cell and is not excreted from it, so long as the cell is 

 intact, but only passes out after the cells have been crushed into frag- 

 ments. Whilst the cell is alive and intact it absorbs the sugar into 

 its interior, breaks it up there, and forms the alcohol which is 

 afterward excreted. 



To make this clearer I may perhaps be allowed to use a very crude 



