68 PHYSIOLOGICAL MORPHOLOGY 



the aldehyde groups which it contains. These are, however, speculations to which 

 neither chemistry nor physiology lend support 1 . 



The method of silver-reduction which Loew and Bokorny employed is not, as 

 they suppose, a specific test for aldehydes 2 . In certain cases, the reducing substances 

 are not proteids at all, while the disappearance of the power of reduction after 

 death is frequently merely due to an exosmosis of the substances in question. 

 If by treatment with caffein, antipyrin, ammonium carbonate, aniline dyes, &c., 

 a dead cell is caused to retain these reducing substances, a granular reduction- 

 precipitate is formed when a solution of silver is added. These granules are called 

 by Loew and Bokorny, ' Proteosomes,' and regarded by them as a sure sign of the 

 presence of active albumin. (See the quoted works of 1891 and 1895.) Since, 

 however, the granular precipitations formed by caffein, &c., partly retain their 

 reducing powers after being boiled, they can hardly be characterized by that 

 lability and tendency to decomposition which Loew and Bokorny state to be an 

 essential property of their active albumin 3 . 



Loew and Bokorny now indeed admit that these reducing substances are 

 commonly present only in the cell-sap, and see in their 'active albumin' not 

 a component of living plasma, as they originally maintained, but simply a substance 

 of importance in metabolism. No further attention need therefore be given to 

 the suggestion that in active albumin we have the directive and decisive agent in 

 originating vital processes. For in every case the inherent nature, structure, and 

 organization of the protoplasm are of paramount importance for all vital phe- 

 nomena, and the knowledge that particular food substances are necessary for its 

 growth and maintenance, as indeed must necessarily be the case, gives us but 

 little or no deeper insight into its internal mechanism, or into the causes which 

 affect and govern this mechanism. 



Since the precipitations which, according to Loew and Bokorny, are a certain 

 test for the presence of active albumin, are apparently not produced in many 

 plants, it is impossible that these reducing substances can have any such general 

 and essential importance as Loew and Bokorny originally supposed. For since it 

 may be readily proved that the caffein and other substances do actually penetrate 

 the plasma and appear in the cell-sap, it follows that the non-formation of any 

 precipitate is due to the absence of the reducing substances. A more direct proof 

 that the active albumin does not form an essential part of the living plasma is 

 afforded by the fact that cells in which the 'active albumin' is kept permanently 

 precipitated by caffein, &c., remain living and capable of active growth. 



The chemical nature of the bodies in question is therefore immaterial to the 

 point at issue. In certain cases, no proteid substance can be detected in the 

 precipitated ' proteosomes,' while similar granular precipitates may be produced 



1 Loew und Bokorny, Die chemischen Kraftquellen im lebenden Protoplasma, 1882; Biol. 

 Centralbl., 1891, Bd. xi, p. 5; Flora, 1896, p. 68, &c. Cf. Pfeffer, Flora, 1889, p. 46; Klemm, 

 Flora, 1892, p. 395, and Ber. d. Bot. Ges., 1892, p. 237 ; Zimmermann. Beihefte z. Bot. 

 Centralbl., 1893, Bd. in, p. 323, and the literature here cited. 



a See Baumann, Pfliiger's Archiv f. Physiol., 1882, Bd. xxix, p. 400. 



3 See Correns. Jahrbuch f. wiss Bot., 1894, Bd. XXVI. p. 641. 



