SURFACE TENSION HYPOTHESES 289 



(%) Hypotheses relating to Surface Tension — BertJwld, 

 Quincke 



It has already beea occasionally pointed out here and 

 there, that in bringing about protoplasmic movements the 

 phenomena of the so-called surface tension of the fluids may 

 play a part. 



Hofmeister attempted, as far back as 1867, to interpret 

 the so-called rounding off of drops of protoplasm, which 

 has often been regarded as a phenomenon of contraction, 

 as a property identical with the tendency to assume a 

 spherical form in ordinary drops of fluid, that is to say, as 

 an effect of the surface tension. 



Engelmann also, on the ground of his idea that proto- 

 plasm becomes fluid by electrical stimulation, arrived (1869) 

 at the view that the forces which cause the contraction of 

 protoplasm "may be just the same as those which tend 

 to make every non- spherical free drop of fluid become 

 spherical " ; that would, of course, be the surface tension.- 

 He is, with Hofmeister, completely convinced of the fact 

 that contractions, in the ordinary sense, are not the cause of 

 movements, and agrees entirely with the view of the latter 

 concerning the extension of the currents backwards. At 

 a later date, howevei, Engelmann did not recur again 

 to this, in my opinion, very correct idea, but developed, as 

 we have seen, a theory of movement based on essentially 

 other grounds. 



In 1876 I tried to make use of surface tension 

 hypothetically as the efficient cause in the explanation of 

 cell division. As I have already remarked, I regard the 

 explanation given then as still suitable in its main points, 

 and indeed as having become considerably more probable 

 from recent observations with regard to the great part played 

 by surface tension as an important cause of the processes 

 of movement in protoplasm. Since the time when I first 

 arrived at the conviction that this property of fluid bodies 

 must be of pre-eminent importance for the explanation of 

 the changes in form exhibited by fluid protoplasm, I have 



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