lUl 



thereafter directly in 1 o/o gold chloride solution for nbouL 5 

 minutes; then washed quickly in distilled water and put 

 back inlo a sohilion consisting- of efjual volumes of formic 

 acid and water for another 24 hours, also in tlie (hu-k; 

 after this wasliing, dehych'ated in the usual way and mounted 

 in balsam. This method showed a great advantage in that, 

 iiy treating with acid, all the culture medium disappeared 

 and only the tissue was left adhering to the coverglass. The 

 clot was brought into solution as acid albumins by the 

 formic acid. This is a great advantage because the clot 

 always hinders more or less in finer microscopic exa- 

 minations and especially when ordinary anilin dyes were 

 used, the clot itself absorbed the stain and the contrast 

 between the tissue cells and clot was less pronounced. For 

 photographic purposes this method proved most excellent. 

 No precipitation occurred, the cells were clean, and con- 

 trast}^ as if they were washed clean from all substance 

 save the cells themselves. 



The cells appeared reddish, more or less deep coloured, 

 granules deeply stained and vacuoles and nuclei pretty clear 

 and unstained. The outlines of the cells were usually in the 

 most perfect condition and the finest, tiniest processes and 

 connections in between the cells coidd be distinguished very 

 sharply. 



By using L 6 w i t's method as described above there were 

 some disadvantages. In most cases the dissolution of tne clot 

 was so vigorous that often the cells disappeared at the 

 same time; therefore I modified the method. The successful 

 preparation dei)ends very much upon the location of the 

 tissue in the clot; if the tissue is located near the free sur- 

 face or in the middle of the clot, it will easily be washed 

 awaj^, when the clot is dissolved, but if the tissue is located 

 near the bottom of the clot, i. e., close to the glass, it sticks 

 to it and remains. The preparation method was modified in 

 the following way. Instead of using the concentrated Formic 

 acid as a fixative, it was used as a 50 o/o solution and the so- 



