RESPIRATION AND FERMENTATION 131 



Suggested Experiment. Prepare two sets, each of 10 seeds, of Farley 

 or Oats, and weigh to a milligram; soak one set some 10 hours or more 

 and place it in the chamber of a respirometer (not first germinating them 

 elsewhere, which would entail some unmeasured loss of carbon dioxide), 

 and supply caustic potash in the measuring-tube. Supply favorable ger- 

 mination conditions until the caustic potash has risen to near its limit, then 

 determine exactly the volume of the carbon dioxide and the dry weight of 

 the germinating seeds. In drying the latter also dry the other set of seeds, 

 and use their percentage of moisture for determining the original dry weight 

 of the germinated set, whence the actual loss of dry substance therein may 

 be ascertained. Treating this substance, rather conventionally, as starch, 

 and, using the formula C H I0 O 5 + 6O 2 =6CO 2 -l-5H 2 O, ^determine whether 

 the starch used and the carbon dioxide formed agree when properly figured 

 upon a molecular-weight basis. 



The results of this experiment, despite its imperfections, 

 will aid to confirm the supposition indicated by the earlier 

 experiments, that respiration in these seeds exhibits phenomena 

 seemingly reciprocal to those of photosynthesis; and they seem 

 further to indicate that there must exist an equation, the re- 

 ciprocal of the photosynthetic equation, which has the form 

 C 6 H 12 6 + 60 2 = 6C0 2 + 6H 2 0. This may be termed the 

 conventional respiratory equation, and, among all the chemical 

 expressions ■ of organic nature, it is second in importance only 

 to the photosynthetic equation. But the student must here 

 be warned that this equation, while it expresses the end result 

 of the process, is by no means true for the immediate steps, 

 which are vastly more complex than the formula suggests. 



"In the foregoing experiments germinating seeds were used 

 as representatives of working tissues chiefly because of their 

 convenience of manipulation in conjunction with their conspicu- 

 ous activity. Moreover these particular kinds were deliber- 

 ately selected because they are known to exhibit the gas exchanges 

 in the simplest and theoretically most perfect ratio, namely, 

 that in which the volumes of the gases absorbed and released 

 are equal. In other tissues, however, and especially in many 

 other seeds, this simplest ratio by no means always holds (and 

 indeed it is a question whether in the seeds above recommended 

 the ratio is not simply accidentally correct), and the student 

 should now make himself acquainted with this phase of the 



