82 CRITIQUES AND ADDRESSES. [iv. 



exemplified by supposing the sugar to be a card-house. 

 According to Stahl, the ferment is somebody who knocks 

 the table, and shakes the card-house down ; according to 

 Fabroni, the ferment takes out some cards, but puts 

 others in their places ; according to Thenard, the ferment 

 simply takes a card out of the bottom story, the result 

 of which is that all the others fall. 



As chemistry advanced, facts came to light which put 

 a new face upon Stahl's hypothesis, and gave it a safer 

 foundation than it previously possessed. The general 

 nature of these phenomena may be thus stated : A body, 



A, without giving to, or taking from, another body, 



B, any material particles, causes B to decompose into 

 other substances, C, D, E, the sum of the weights of 

 which is equal to the weight of B, which decomposes. 



Thus, bitter almonds contain two substances, amyg- 

 dalin and synaptase, which can be extracted, in a separate 

 state, from the bitter almonds. The amygdalin thus 

 obtained, if dissolved in water, undergoes no change ; 

 but if a little synaptase be added to the solution, the 

 amygdalin splits up into bitter almond oil, prussic acid, 

 and a kind of sugar. 



A short time after Cagniard de la Tour discovered the 

 yeast plant, Liebig, struck with the similarity between 

 this and other such processes and the fermentation of 

 sugar, put forward the hypothesis that yeast contains a 

 substance which acts upon sugar, as synaptase acts upon 

 amygdalin. And as the synaptase is certainly neither 

 organized nor alive, but a mere chemical substance, 

 Liebig treated Cagniard de la Tour's discovery with no 

 small contempt, and, from that time to the present, has 

 steadily repudiated the notion that the decomposition of 

 the sugar is, in any sense, the result of the vital activity 

 of the Torula. But, though the notion that the Torula 

 is a creature which eats sugar and excretes carbonic acid 



