306 



LECTURE XIV. 



The above determinations were made by means of the apparatus 

 shewn in Fig. 38. A is a graduated glass bell-jar standing in a saucer 

 which contains water : B is a thermometer, fastened by a cork in the 

 neck of A, with its bulb in contact with the spadix which is supported in 

 a test-tube C filled with moist sand : the bulb of the thermometer and the 

 spadix are covered by a piece of muslin. The internal surface of the 

 bell-jar is smeared with concentrated solution of potash : hence the CO 2 

 evolved by the spadix is absorbed, and the absorption of oxygen can be 

 estimated by the rise of the water from the saucer into the graduated 

 bell-jar. 



FIG. 38 (after Garreau). 



But the evolution of heat is not confined to those pro- 

 cesses of destructive metabolism in which oxygen is con- 

 cerned ; it accompanies others as well. We have an instance 

 above, in Eriksson's experiments, of the evolution of heat 

 in the absence of oxygen. One of the most conspicuous 

 examples of destructive metabolism in the absence of oxy- 

 gen is, as we have seen (p. 208), the alcoholic fermentation 

 effected by Yeast. The fact that a liquid in which this 

 fermentation is going on soon acquires a temperature con- 

 siderably higher than that of the surrounding air has long 

 been known, but Eriksson has shewn definitely that this 

 rise of temperature takes place also in the absence of 

 oxygen, that it is due, therefore, to the fermentative activity 

 of the Yeast. 



Two bottles were taken, and the one filled with water, the other with 

 a fermenting solution of sugar ; the temperature of the liquid in each 



