82 PROTOPLASM 



9. Remarks upon Frommann's Experiments on Drops of 

 Oil-Foam 



Frommann published in 1890 some communications 

 concerning experiments which he performed on drops of oil- 

 lather prepared according to my directions, and upon which 

 I feel myself bound to express an opinion. I must say 

 beforehand, however, that I am only able to do this with 

 some difficulty, since Frommann's statements are in great 

 measure insufficiently clear to me. I therefore take two 

 points in them, which at least go . to the root of the 

 author's case in his remarks directed against me. On p. 

 666 et seg/., Frommann tries to show that " in drops with 

 non-fluid contents" a perfect alveolar structure is no longer 

 present, and that both the walls of the alveoli and the outer 

 limiting layer of such drops are interrupted in many places 

 by gaps. Although Frommann unfortunately does not state 

 more accurately what he understands by " drops with non- 

 fluid contents," and how he manufactured them, I must 

 suppose that he means by the expression foams which are 

 manufactured from very much thickened and viscid oil, 

 such as I also have described above. Since such foams 

 spoil relatively quickly, and their framework of oil pos- 

 sesses at the same time a very tough consistency, I will by 

 no means dispute that during their gradual degeneration 

 gaps may appear in the walls of their alveoli, although I 

 never myself observed anything of the kind in the. 

 viscid and immobile foams investigated by me (see before, 

 pp. 20 and 44). As has been stated in the preceding 

 sections, I have principally directed my attention hitherto 

 to completely fluid foams, in which the formation of such 

 gaps is simply a physical impossibility. Frommann seems 

 inclined to dispute even this fundamental law of physics, 

 since he states on p. 667 : "Numerous gaps in the walls of 

 the vacuoles, leading to a disappearance of the vacuolar 

 structure, may also be obtained in drops of an emulsion 

 which is prepared without K 2 C0 3 merely by rubbing up a 

 drop of linseed oil with water. The drops prove to be 

 more or less regularly and thickly vacuolated, the walls of 



