8 PROTOPLASM 



before he published his hypothesis of protoplasmic movement. 

 In his communication of 1888, Quincke still treats protoplasm as 

 a simple fluid, and nowhere speaks of its froth-like structure. 

 When he lays stress (1889), after the publication of my iirst report 

 (1889), on the frothy structure, I can only recognise in this 

 fact the influence of my experience, although he nowhere men- 

 tions this in his publication, which deals with protoplasm and the 

 phenomena of movement exhibited by it. 



The train of reasoning which led to the experiments with 

 fatty oils was as follows. If a mixture of oil and very finely 

 ground down particles of a substance easily soluble in water, 

 be brought into water, the latter will enter by diffusion into 

 the oil. The fine particles of soluble substance will attract 

 the water and become converted into minute drops of a 

 watery solution. The closely-compressed drops are able to 

 convert the oil in which they are suspended into a fine froth 

 in this manner. Although this reasoning did not prove 

 perfectly correct, yet the experiments prompted by it led to 

 gratifying results. 



OKve oil that had stood for a long time in a bottle in 

 the laboratory was first employed for the experiments. As 

 soluble substances, common salt, cane sugar, and potassium 

 nitrate were tried. The method pursued was as follows. 

 A very small quantity of the soluble substance, taken on the 

 tip of a knife, was pulverised as finely as possible in a small 

 mortar, and then rubbed up into a thick paste with a drop 

 of olive oil. Small or minute drops of this mixture were 

 placed on a cover-slip provided with wax feet at the corners, 

 and the cover-slip was then inverted over a drop of water 

 of sufficient size upon a slide. As a rule, the ordinary 

 Heidelberg tap-water was used, which contains relatively 

 little dissolved matter, but sometimes distilled water was 

 also tried. But since the experiments gave similar results 

 in both cases, the ordinary town water was used in con- 

 sequence exclusively. The wax feet on the cover-slip were, 

 as a rule, high enough for the drops of the oil mixture 

 to be in contact with the surface of the slide without, how- 

 ever, being compressed. 



In the manner described, it was possible, to convert the 



