170 



A TEXTBOOK OF BOTAXY 



[Oh. IV, 



i'lij. 117. — A I'aloriscope ; X 5. I'ho two 

 Dewar bulbs have doul>le walls with a vacuum 

 between (as familiar in "Thermos" l^ottles), and 

 hence prevent loss of heat. The respiring tissue to 

 be tested is divided into two parts, and placed in 

 the two . flasks, but is immediately killed in one. 

 Thus the delicate thermometers are made to record 

 within a few hours the degree of boat released by 

 the respiration of the living tissues. 



litliiiil in the 

 Hask is found to 

 contain a con- 

 siderable quan- 

 tity of alcohol, 

 together with 

 small amounts of 

 other substances 

 known to be 

 formed by the 

 activity of the 

 Yeast, which all 

 this time is in 

 vigorous growth 

 and multiplica- 

 tion. If certain 

 mineral salts, es- 

 sential to the 

 metabolism of 

 the Yeast, are 

 present, the pro- 

 cess continues 

 until the sugar 

 is exhausted, or 

 else until the in- 

 creasing tiuanti- 

 ties of alcohol in- 

 hibit the further 

 growth of the 

 Yeast. Thus, un- 

 der experimental 

 conditions, the 

 Y(>ast i.ilant in 

 its growth fer- 

 ments su,gar to 

 carbon dioxide 



