200 LECTURE XI. 



A consideration of the foregoing figures shews that the 

 absorption of oxygen and the evolution of carbon dioxide are 

 differently affected by variations of the temperature. This 

 may be stated in a general manner thus : that at a low tem- 

 perature the absorption of oxygen is more active than the 

 evolution of carbon dioxide, whereas at a high temperature 

 the absorption of oxygen is less active than the evolution 

 of carbon dioxide. This suggests, and Moissan has actually 

 stated, that for every organ there is, generally speaking, a 

 degree of temperature at which the volumes of the oxygen 

 absorbed and of the carbon dioxide exhaled are equal. 



Although, as we see, the relation between the absorption 

 of oxygen and the exhalation of carbon dioxide is so variable 

 that we may conclude that the one is independent of the 

 other, yet, under normal conditions, the presence of free 

 oxygen promotes certain processes of destructive metabolism 

 of which the exhalation of carbon dioxide is an expression. 

 For example, Wilson has observed that when seedlings are 

 deprived of oxygen, the amount of carbon dioxide which they 

 exhale is diminished, and similar observations have been 

 made by Broughton and by Wortmann. 



We may cite some of the results of these observers in illustration. 

 Wilson experimented with germinating seeds of Lupinus luteus, 

 measuring the CO 2 evolved when the seeds were in air and in hydrogen. 



fist half-hour 57 mgms of CO 2 evolved. 

 I. Period Air \ , 



(2nd 6-6 



II. Period Hydrogen j 3 " 



( 



(4 tn **5 



III. Period-Air (>* ' 3 ' 9 



(6th 57 



The following are some of Wortmann's results which tend to prove 

 the point in question, but which he has interpreted differently. 



i. The mean of a number of experiments made with germinating 

 seeds in the presence or absence of free O, shews that the presence of O 

 promotes the exhalation of CO 2 . 



Average amount of CO 2 evolved by i gramme of seed in i hour in 

 presence of free O, "0995 c.cm. 



Average amount of CO 2 evolved by i gramme of seed in i hour in 

 absence of free O, '0855 c.cm. 



