EXPERIMENTS ON THE PERMEABILITY OF CELLS. 



By J. F. McClendon. 



One of the most important steps in the analysis of life was the discovery 

 of oxygen. Ever since that time it has been known that animals absorb 

 free oxygen and give it out in a combined form. 



The discovery of enzymes has given a clue to the rapidity of oxidation 

 within cells; but enzymes are always present in living substance, and yet 

 oxidation may vary from almost zero in certain eggs and seeds during rest 

 to a high rate during activity. We know that oxidation within muscle is 

 greatly increased during contraction, yet hardly anyone would suppose this 

 to be due to the sudden increase of oxidases. Loeb, however, did use this 

 explanation for the increased oxidation of the egg on fertilization, by sug- 

 gesting that the sperm carries an oxidase into the egg. Certainly the sperm 

 contains an oxidase, as does every other cell, but the sperm is minute in com- 

 parison with the egg, and no one has found any indication of an unusual 

 amount of oxidase in the sperm. Furthermore, the egg may be made to 

 divide by artificial means without the introduction of any enzyme. 



An organism may be caused to absorb more oxygen by any one of a 

 number of different stimuli. But what is stimulation? What is the first 

 change induced in the organism or excised organ by all stimuli? 



Pfeffer showed that stimulation of sensitive plants causes a change in 

 permeability of certain cells (of the pulvinus). This change in permeability 

 causes a change in turgor (internal osmotic pressure) and movement results. 

 The question arises: what relation does this bear to oxidation? According 

 to Ralph Lillie oxidation is suppressed in the cell by the accumulation of 

 waste products to which the resting cell is impermeable. Stimulation 

 increases the permeability of the cell to them and consequently oxidation 

 is increased. Lillie maintained that on fertilization the egg became more 

 permeable, and linked all subsequent phenomena with this change. Not 

 finding any other explanation of the stimulating action of the sperm, I 

 attempted an exact study of the permeability of the egg. 



EXPERIMENTAL. 



Three methods of procedure were followed: (i) the use of cell masses as 

 partitions (on eggs of Lytechinus) ; (2) the use of quantities of eggs sus- 

 pended in a liquid medium (on eggs of Fimdulus) ; (3) experiments on 

 individual eggs (of Arhacia). 



125 



