100 PROFESSOR BUTSCHLI'S 



As you well know already, I use in the preparation of these 

 globules — showing protoplasma-like streaming — ordinary olive 

 oil. My first experiments were made with a small quantity of 

 olive oil which had been standing for along time in my labora- 

 toi'y in a small bottle. By some happy chance this oil had 

 just the right properties which are necessary for the success of 

 the experiment, for not every sort of olive oil is suitable. As 

 far as my experience goes, it tends to show that the ordinary 

 oil cannot be directly used, because it is too thin, or is perhaps 

 deficient in other qualities on which the success of the experi- 

 ment depends. In order, therefore, to prepare a suitable oil, I 

 proceed in the following manner : — A medium-sized watch-glass 

 or flat dish is filled with a thin layer of common olive oil, and 

 is placed on a water-bath or in a small cupboard, such as are 

 used for embedding in paraffine, at a temperature of about 

 50° C, Under the influence of the higher temperature the oil 

 gradually loses its yellow colour and becomes thicker. The 

 great point now is to select the right moment at which the oil 

 will have attained the proper degree of thickness and viscosity, 

 as also the other properties which at present I am not able to 

 define more exactly, but on which much of the success seems 

 to depend. The exact moment can, however, only be found 

 out by systematic trials. After the oil has been thickening for 

 three or four days a trial should be made with a drop of 

 it in the manner described below. Should the drop not 

 become finely vesiculate, and exhibit little or no streaming, 

 continue the heating process and experiment again on the 

 following day. If the oil should have become too thick it will 

 form good frothy drops, but will scarcely show any streaming. 

 In this case mix it with a small quantity of ordinary olive oil, 

 and thus render it more liquid: If it has become much too 

 thick it will form a good froth, but the latter dissolves very 

 rapidly in glycerine. 



You see thus that the process to obtain the suitable oil is 

 somewhat slow, but I do not at present know of any other 

 method by which the result can be arrived at more quickly 

 and surely. 



