973 



cytes may be grouped under the following headings : lo. degeneiation; 

 2o. relation to erythropoësis ; 3o. formation of mononuclear, white 

 bloodcorpuscles ; 4o. formation of thrombocytes. 



III. Material and Methods. 



Provided the material be good, giant-cells, when present, are always 

 demonstrable by every proper staining method. To bring out details 

 well the sections should not be made too thick, because the 

 megakarj'ocytes are large bodies (some, indeed, measure 40fi or more). 

 This is why some experimenters attach value only to sections of 

 3ft at (he most. Some of them achieve the best results with paraffin- 

 sections, but Maximow e.g. asserts that only celloidin material, treated 

 in his own complicated way yields results of any value at all. 

 Others recommend the most various fixation-tluids and dyes. 



In course of time the various fixatives have been abandoned, 

 Zenker's fluid being now used by most researchers, either in its 

 original composition, or slightly modified. 



The dye now generally adopted in staining methods is hematoxylin 

 (EHRLiCH)-eosin and in special cases iron-hematoxylin (Heidenhain)- 

 eosin, besides the various RoMANOwsKi-variations. 



It seemed to me to be best to try these various methods, in order 

 to select the one best suited to my purpose. 



IV. Personal Observations. 



The animal. I experimented upon cat-embryos, young kittens 

 and adult specimens. In view of the problem I wished to solve and 

 the facts known, I confined myself chiefly to young kittens. 



Tissue. Of those kittens which were killed with chloroform and 

 opened immediately (still warm), the spleen, the liver, and the bone- 

 marrow of the femur were excised and put in different fixation-fluids. 



Fixation. With cats Zenker's fluid at =b 37° C. gave most satis- 

 factory results. It yields beautifully fixed preparations and causes 

 the least shrivelling. 



Embedding. Initially the embedding was done in paraffin as well 

 as in celloidin, but when the latter method proved ineffective, it was 

 abandoned and only paraffin was used. 



Sections. These were cut, at a venture, l^i thick, which proved 

 quite effectual, though I also cut some of 3u, which, however, 

 opened up no fresh point of departure. 



Staining. After trying various staining methods subsequent to 

 different fixations, I achieved the best results after Zenker fixation 



68 



Proceedings Royal Acad. Amsterdam. Vol. XX. 



