INTRA-MOLECULAR RESPIRATION. 4OI 



the fact that even m prolonged respiration accompanied by great loss of substance, 

 no loss in nitrogenous assimilated material — i. e. of proteid substances — is to be 

 detected. And this result is so much the more remarkable since we have every 

 reason to assume that it is strictly in the nitrogenous substance of the protoplasm 

 that respiration directly occurs. Like all the vital phenomena of plants, respiration 

 also is brought about by means of the protoplasm : however, the protoplasm only 

 initiates the process, and is not itself injured in constitution by it. 



Some light is thrown upon this remarkable behaviour of the protoplasm in 

 respiration by the recent researches on so-called intra-molecular respiration*. 

 Grischow noticed so long ago as 1819 that in the respiration of Fungfi, more carbon 

 dioxide is occasionally evolved than accords with the oxygen absorbed. In my 

 laboratory, also, other researches showed that occasionally portions of plants of 

 various kinds go on evolving carbon dioxide even when they are unable to take up 

 oxygen. These facts first gained in general interest however when Pfliiger observed 

 in 1875 that frogs not only go on Uving for some time when they remain in an atmo- 

 sphere devoid of oxygen, but they also exhale carbon dioxide. Pfliiger concluded 

 from this that both constituents of this gas must be derived from the organic substance 

 of the frog itself; in other words, that the molecules of the organic substance undergo 

 a decomposition, even without the access of oxygen, of such a kind that atoms 

 of carbon and of oxygen come together within these molecules themselves to form 

 carbon dioxide, which is then exhaled. This process is termed by Pfliiger intra- 

 molecular respiration. There can be no doubt that the evolution of carbon dioxide by 

 plants in a space devoid of oxygen, which has loijg been observed by us, depends on 

 the same process of intra-molecular respiration ; since from all the facts known to us 

 the respiration of plants agrees with that of animals point for point. After having 

 convinced myself that seedlings which remained for days in an atmosphere devoid of 

 oxygen evolved carbon dioxide and ceased to grow, but on being planted in the earth 

 again lived and grew vigorously, I requested Dr. Wortmann in 1878 to undertake a 

 thorough investigation of this question in my laboratory. This was done with skill 

 and judgment. His experiments with seedlings, flowers, and growing stems were made 

 for the most part in the Torricellian vacuum, and yielded the following important 

 results : i. the intra-molecular respiration during the first few hours yields just as much 

 carbon dioxide as does respiration under the influence of the atmosphere containing 

 oxygen: 2. the energy of the intra-molecular respiration sinks considerably, even 

 after a few Jiours, thus showing an abnormal condition of the plant as contrasted 

 with normal respiration. This fact is, I believe, decidedly opposed to the view 

 established by PfefFer, to the effect that respiration is identical with alcoholic 

 fermentation. This view is, of course, supported by the fact that the most various 

 parts of plants on being excluded from oxygen, produce small quantities of alcohol, 

 besides disengaging carbon dioxide. But, apart from the fact that this production 



' On intra-molecular respiration cf. Pfeffer, ' Z>as Wesen und die Bedeutung der Athmung in 

 der PJlanze^ in 'Landw. Jahrb.' (Berlin, 1878). Julius Wortmann, ' Uber die Beaiehung der intra- 

 moleculare zur normalen Athmung der P/ianzen,' in ' Arb. d. hot. Inst, zu Wiirzburg' (1879), II. B, 

 p. 500, Eriksson, ' Uber Wdrniebildung durch intramoleculare Athmung^ in * Untetsuchungen aus 

 dem bot. Inst, zu Tubingen' (Leipzig", 1881). 



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