CYTOLOGICAL METHODS. 361 



bichromate than those which are given by fixation with acids. 

 The acids contract them somewhat, and so give them sharper 

 outlines,, and thus render them individually distinguishable. 

 The resulting image thus becomes clearer, but I do not 

 admit that it is in all cases more lifelike.) 



The fixatives chiefly employed for nuclei are liquid of 

 Flemming and liquid of Hermann. For most purposes I think 

 they are as good as anything that has hitherto been imagined. 

 There is a slight difference between them. Liquid of Her- 

 mann, owing to the platinum chloride, causes chromatin to 

 shrink more than liquid of Flemming does, and thus often 

 gives clearer images of chromosomes, especially of their 

 splitting. 



But it is a mistake to suppose that equally good images 

 cannot be obtained by means of other reagents. Some of the 

 finest chromosomes I have seen have been fixed with Lindsay 

 Johnson's mixture ( 49), and liquid of Tellyesniczkv has 

 given me others nearly if not quite as good. 



Though I have not found anything superior to these, I do 

 not mean to imply that there are not others as good or nearly 

 as good. Very likely there are ; for the nucleus is by far 

 the easiest thing in the cell to fix (/. v. so far as chromatin 

 and nucleoli are concerned ; I have left the caryoplasm, or 

 whatever else there may be in a nucleus, out of account, as 

 next to nothing is known concerning it) . Mixture of Grilson- 

 Carnoy-Lebrun gives very fair nuclei indeed, and will be found 

 highly useful where very great penetration is required. 



^.6- regards the cytoplasm. Cytoplasm is made up of two 

 elements, a fibrillar network the spongioplasm, reticulum, 

 or mitome ; and a more or less granular liquid that bathes 

 it the hyaloplasm or enchylema. It does not follow that 

 a reagent that will fix one of these will also fix the other. 

 Nor does it follow that if both are fixed you have of 

 necessity a perfect fixation, for that depends on the object 

 in view. 



If you fix both, you will have a full fixation; biat in that 

 case the granules of the hyaloplasm (be they vital, or be they 

 only " precipitation forms," see 27 A), and the secretions 

 or other inclosures that may be present in it, may so mask 

 the fibrils of the spongioplasm as to interfere with the 

 observation of it. So that if the latter is the principal 



