268 THE POWER OF RESISTANCE TO EXTREMES 



Nencki l suggests that tox-albumins act catalytically like enzymes, and it 

 is certain that a protoplast must die if some of its essential constituents 

 are decomposed by the penetration of a proteolytic enzyme. It is also 

 possible that the catalytic acceleration or retardation of one or more 

 partial functions might produce disturbances leading to death. In fact a sub- 

 stance may act in some such way as a powerful poison, without combining 

 with the protoplasm or entering into metabolism. The poisonous aniline 

 dyes are not assimilated, and the same probably applies to most poisonous 

 alkaloids 2 and to chloroform. 



The action of acids is mainly due to the fact that they form salts with 

 substances connected in some way or other with the living protoplasm 3 . An 

 active acid produces a granular precipitate of proteids, and destroys the plasticity 

 of the protoplasm even when in great dilution 4 . The known properties of proteids 

 lend support to the view, that alkalies produce swelling and solution in the 

 protoplasmic constituents. 



The poisonous heavy metals probably act by entering into combination with 

 constituent proteids 5 . In addition formic aldehyde and other substances which 

 react energetically with proteids act as strong poisons, provided that they are able 

 to penetrate the protoplast. 



Chloroform, ether, alkaloids, and aniline dyes do not form fixed compounds, 

 since they are rapidly removed on immersal in water. This can be repeated 

 several times by using very dilute solutions of methyl violet or of cyanin 6 . The 

 fact that the dye accumulates especially rapidly in certain regions of the cytoplasm 

 affords no clue as to its mode of action. It is even uncertain whether the fixation 

 is physical or chemical in nature, for by means of dissociation and mass-action 

 combined pigments and other substances may be soaked out of the cell 7 . Many 

 of these substances may enter into loose combinations like that of carbon monoxide 

 with haemoglobin, and gradually accumulating may affect some essential material 

 normally present 8 . If in a particular species the conditions for such a reaction do 

 not exist, then the poison in question would be innocuous in this case. The 

 fact that enzymes may leave the negative and positive varieties of a fermentable 

 substance untouched, shows that a trifling dissimilarity of structure or composition 

 may enable closely related protoplasts to react dissimilarly to particular poisons. 



1 Cf. Loew, System d. Giftwirkungen, 1893, p. 68. 



2 [Admirably shown by immersing Elodea in dilute veratrine nitrate, when the nitric acid is 

 slowly absorbed and the veratrine precipitated. Penicillitim can assimilate various alkaloids. 

 Cf. Ewart, On the Physics and Physiology of Protoplasmic Streaming, Clar. Press, 1903, pp. 84, 85.] 



3 The protoplasm need not always be alkaline. 



4 Klemm, Jahrb. f. wiss. Bot., 1895, Bd. xxvni, p. 658. The destructive action of con- 

 centrated acids and alkalies does not concern us. 



5 Kunkel, Handbuch d. Toxicologie, 1890, p. 118. 



6 Pfeffer, Unters. a. d. Bot. Inst. zu Tubingen, 1886, Bd. II, p. 252. 



7 The theory that chloroform combines with the lecithin constituents of the protoplasm is based 

 upon the solubility of chloroform in this and other oily substances. Cf. Kunkel, 1. c., p. 386 ; 

 Overton, Studien iiber Narkose, 1901. 



8 Potassium may in certain cases be displaced by sodium. 



