TEMPERATURE AND MOVEMENT 79 



contained in the alveoli, and its absorption into the surround- 

 ing fluid, which must be the cause, and as soon as a complete 

 equalisation has taken place the streaming must be definitely 

 put an end to. Unfortunately I have not troubled to find out 

 whether, as is probable, one can produce new streamings in 

 drops which have streamed themselves out by replacing the 

 soapy glycerine around them with fresh glycerine. 1 On the 

 other hand, I tried to stir up afresh drops which had come 

 to rest by bringing them into a 1 per cent solution of K 2 C0 3 . 

 After the drops had remained some hours in this solution, 

 and had again become quite opaque, they passed a second 

 time into active streaming movements after being washed 

 out and having semi-dilute glycerine added to them ; the 

 alveoli had been again filled with soap solution. On the 

 other hand, a similar attempt to effect the renewal by means 

 of a 1 per cent solution of Venetian soap did not succeed 

 well, since the froth-drops were quite spoiled by it. I think, 

 however, that one might obtain better results with a more 

 dilute soap solution. 



As we found before, a heightened temperature causes a 

 considerable increase in the intensity of the streaming and 

 in the forward movement. The cause of this phenomenon 

 is to be sought in the fact that the viscid oil becomes more 

 fluid at a higher temperature, of which fact it is easy to 

 convince oneself with viscid oil. The greater fluidity of the 

 oil will permit of not only an intenser current under the 

 action of an equal force, but also no doubt of the easier 

 bursting of the alveoli, which must favour the phenomena 

 of movement. 



Mensbrugghe is of opinion (1890-91) that the strengthening 

 of the phenomena of movement by an increase of temperature 

 depends on a greater intensity of the chemical reaction, which 

 he assumes as the cause of the phenomena of streaming. For 

 this very reason he considers the explanation given by me as 

 erroneous. But although, as experience teaches, surface tension 

 is in general diminished by raising the temperature, this fact is 



1 Since sending off the manuscript I have several times seen new stream- 

 ings arise as the result of adding fresh glycerine to drops which had ceased to 

 stream for a long time. 



