B 



y 



lOfa 



FIG. 9. Sections of the testis of the mouse, to show good and bad 

 fixation. Both are 8/x paraffin sections dyed with Hansen's 



haematein.^^ 



A, fixed with Allen's 'B.15'.^ Grade I fixation. B, fixed with osmium tetroxide, 

 i^o, buffered at pH 7-4. Grade V fixation. (With methacrylate embedding, the 

 same fluid gives good fixation for electron microscopy.) 



