510 ('. CLIFFORD DOBELT.. 



must be done with care ; if this is the case, harmful effects 

 do not result from subsequent drving sifter staining. Minchin^ 

 has found a similar method suitable for studying the structure 

 of trjpanosomes. I have also obtained excellent preparations 

 of these and hasmogregariues, etc., in this w;iy. 



I also made dry film preparations, fixed in absolute alcohol 

 and stained by Giemsa^s method in the usual way. This 

 method gives rise to most misleading appearances in the 

 organisms, but these are of considerable interest for com- 

 parison with those in other preparations which liave l)een 

 properly fixed. 



The appearances ol)sei-vable in different preparations will 

 be considered later, but it may be noted here that they vary 

 accordino" to the leno-th of time during which the osmic 

 vapour is allowed to act, and according to the degree to 

 which the stain is extracted with alcohol after staining. 



During my stay in Trincomalee, I was unable to use other 

 methods of fixation and staining. But from my previous 

 experience of the method I employed, I believe that m}^ pre- 

 parations are trustworthy, and give reliable information 

 regarding the structure of the organisms. Comparison of 

 my results with those of others has served to strengthen this 

 opinion. 



In all cases the films were made from the crystalline style 

 immediately after removal. Cristispirae usually undergo 

 degenerative changes soon after they have been removed 

 from their host, and therefore exhibit a structure which is 

 very different from that of normal individuals. It is true 

 that the}' will often live in carefully made preparations for 

 several hours. But their motility, as a i-ule, diminishes 

 rapidly, and their internal and external structure becomes 

 modified by degenerative changes. 



1 E. A. Miiieliiii. "The Structure of Trypanosoma lewisi in 

 Relation to Microscopical Technique."" ' Quart. Journ. Micr. Sci.,' voi. 

 r,:i, 1909. p. 755. 



