RESPIRATION 21 



oxidizing ferrous compounds, presumably ferrous oxide to 

 ferric oxide.* 



Other bacteria may be discovered which, needing carbon 

 and nitrogen compounds only to supply the constructive 

 elements of protoplasm, obtain energy by oxidizing other 

 substances present in solution in the waters in which they 

 live, and therefrom absorbed into their own bodies. 



The^essential product of respiration, the one which dis- 

 tinguishes ilTTrom all the other functions of the living or- 

 ganism, jsjdyaetie energy . The material products vary in 

 kind and in quantity according to the nature of the organ- 

 ism and the substances which can be affected. Ordinarily 

 these substances are complex compounds elaborated within 

 the body of the respiring plant. That this is not essen- 

 tial is shown by the successful existence of bacteria which 

 oxidize nitrogen, sulphur, iron, and possibly compounds of 

 other elements. These, though necessarily absorbed before 

 they can be acted upon, are not first elaborated by the cell. 



Free oxygen is not necessary to all organisms or to all 

 cells. The haemoglobin of the blood is a complex com- 

 pound from which some of the oxygen, only loosely held, 

 can be readily given off where oxidation for the supply of 

 energy is needed. Similarly the color products of certain 

 bacteria (e.g., Bacillus brunneus) are reserves of oxygen 

 which become used when there is no longer an adequate 

 supply of free oxygen. f From colorless compounds also, 

 the cells at depths in the tissues of animals (perhaps also 

 of plants^), to which free oxygen penetrates only in in- 

 sufficient amounts if at all, obtain by decomposition the 

 energy needed. These decompositions are not necessarily 



* Winogradsky, S. Uber Eisenbakterien. Bot. Zeitung, 1888. Molisch, 

 H. Die Pflanze in ihren Beziehungen zum Eisen, Jena, 1892. See also 

 Miyoski, M. Studien iiber die Schwefelrasenbildung und die Schwefel- 

 bacterien der Thermen von Yumoto bei Nikko and Uber das massenhafte 

 Vorkommen von Eisenbacterien in den Thermen von Ikao. Journal Coll. 

 Science, Imp. Univ.. Tokyo, vol. X., pt. II., 1897. 



\ Ewart, A. J. On the evolution of oxygen from colored bacteria. Jour- 

 nal of the Linnean Society, XXXIII., p. 123, 1897. 



t Pfeffer, W. Berichte der Math-phys. Classe der Konigl. Sachs. 

 der Wissensch. zu Leipzig, 27 Juli, 1896, p. 383. 



