W. F. LOOMIS 



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would exist around a spherical cell that produced an diffusible meta- 

 bolite [10]. Figure 5 presents his results as applied to pCOa- Clearly the 

 curve of pCOo is highest in the centre of the postulated cell and drops in 

 hyperbolic fashion towards the periphery. A further drop at the cell 

 membrane then occurs that is dependent on the permeability of the meta- 

 bolite in question. Since we know that fatty cell membranes are more 

 permeable to CO2 than to oxygen or even water, this second part of the 

 curve may be essentially eliminated from consideration in the case of COg. 

 Outside the wall appears a third gradient that I refer to as the "blue 



Fig. 5. Gradient of pCO., in a spherical cell or cell aggregate: q = respiratory 

 rate ; Z), = rate on internal diffusion (or cell streaming) ; £), rate of external diffusion 

 (or convectional streaming) ; h = permeability of the membrane and r^ = radius of 

 cell or cell aggregate. Modified from Rachevsky [10]. 



haze" effect, for it makes me think of the quiet lounge of some London 

 club where three older members are reading their newspapers, each 

 member surrounded by a blue haze of pipe smoke that he has produced 

 himself. Clearly any analysis of the smoke within the room that first 

 allowed it to become mixed would not give a correct idea of the smoke 

 concentration to which each club member had been exposed all afternoon. 

 Rachevsky 's third or blue-haze gradient therefore reflects the degree of 

 stagnation within the system. Whenever extracellular currents exist, no 

 external gradients can form, while simple stagnation reacts upon a system 

 so as to increase the final level of pCO.^ existing at the centre of the 

 respiring mass. 



