592 PRINCIPLES OF GENERAL PHYSIOLOGY 



the scale of Barcroft's apparatus, and an evolution of 25 mm. of carbon dioxide. 

 In the presence of m/6,000 potassium cyanide, the same heart performed more 

 work (1,380 g.-cm.) with the consumption of only 8 mm. of oxygen, and 

 gave off 9 mm. of carbon dioxide. On p. 143, it is shown that the excitability 

 of the heart to electrical stimuli, even when the consumption of oxygen has been 

 completely abolished by m/2,000 cyanide, is unchanged. 



The explanation given by Warburg of the action of cyanide will be found 

 immediately. 



Relation to Catalysts. Warburg and Meyerhof (see Warburg, 1914, p. 334) 

 have obtained results with unfertilised, cytolysed sea urchin eggs which show the 

 importance of iron. The ash of the eggs was found to contain considerable 

 amounts of iron. The addition of iron salts to the egg substance caused very 

 considerable increase in the oxygen consumption, an effect not produced by other 

 metallic salts, not even by manganese. 



Alcohol extracts were also made, evaporated to dryness, and the residue 

 extracted with ether. A part remained undissolved, and this part consumed no 

 oxygen, even on the addition of iron salt. The ether extract was evaporated, and 

 the residue suspended in water. This suspension, by itself, consumed no oxygen, 

 but, on addition of iron, the oxidation amounted to as much as that of the original 

 egg substance. Substances of a "lipoid" nature are, therefore, responsible for 

 the phenomenon. 



Now, Thunberg (1911) has observed that lecithin, in the presence of iron, 

 consumes oxygen at a considerable rate; and lecithin is present in the eggs. 

 Further, we have seen reason, in preceding pages of this chapter, to hold that the 

 activity of the peroxidases of the cell depends on their content in iron (or 

 manganese). But, since lecithin is not, to any perceptible degree, autoxidisable, 

 the origin of the cell peroxides remains, as yet, unexplained. A further difficulty 

 is the absence of carbon dioxide production, both in the cytolysed eggs and in the 

 action of iron salts on lecithin. 



According to information given me by Dr Weizsiicker, Warburg has recently 

 found that the amount of potassium cyanide required to stop oxidation in the egg 

 cells of the sea urchin is precisely, equal to that required to combine with the iron 

 which they contain. This fact distinctly points to the iron as the catalyst 

 concerned in oxidation. It is difficult, however, to see exactly what compound of 

 iron, containing cyanide ion, could be reversible under the conditions of the 

 life of the cell. It must be a complex ion of the nature of the ferrocyanic ion ; 

 but it is not a simple process to recover the iron from such compounds under 

 conditions which would be possible in a protoplasmic system. 



Vernon (1914, p. 220) points out that the indophenol oxidase is inhibited by 

 narcotics in a series closely corresponding to their anaesthetic action on tadpoles, and 

 draws the conclusion that the oxidation process is connected with lipoids. He 

 shows that nucleo-proteins have nothing to do with it. 



Mode of Action of "Structure." Warburg (1914, p. 337) suggests that the 

 essential importance of structure consists in the presence of surfaces for condensa- 

 tion of the catalysts active in the cell processes ; in other words, for adsorption. 

 The action of narcotics of the alcohol series is much greater on the fermentative 

 power of yeast cells than on that of the press juice, apparently because these 

 substances are highly adsorbed and drive off the enzymes from their state of 

 condensation on the surfaces (see the paper by Warburg, 1913, 1, p. 20). 



This observer does not think that the view of separate " reaction-chambers," 

 although it may apply to other chemical reactions in the cell, is applicable to the 

 case of oxidation, because the fluid contents presumably contained in these spaces 

 can be changed by diffusion in certain cases, without affecting the oxidation 

 processes. It does not appear to me, however, that the evidence is sufficiently 

 convincing to show that the essential contents were actually changed in these 

 instances. The active contents of the hypothetical, ultra-microscopic vacuoles 

 might be indiffusible, or held by adsorption. Probably both surface condensation 

 and microscopic reaction-chambers play a part. 



There are some further experiments by Warburg (1913, 2), which require 



