THE MICROTOMIST 'S VADE-MECUM

Palladium chloride.                                 suIl O
Silver nitrate (in strong solutions).               riolO
Osmic acid in solution.                              1he fOlk
Gold chloride.                                      kg ind ji
Perchloride of iron.                                 Ossica
It is not intended to be asserted that the quality of the      @ein1
carmine stain is necessarily seriously impaired by the use of   TevvbrtCt
these fixatives, but merely that they make staining uncertain,   isit0 CO
and sometimes, as in the case of chromic acid, so difficult of   hbojoio
attainment by carmine or hematoxylin that the operator is      tpoostr
driven to one of the anilin colours. Osmic acid comes into       dt,
this category on account of its tendency to overblacken, and      hI the
of the obstinacy with which it remains fixed in the tissues      gaCh
when used in solution.
It may be stated that, as a general rule, the reagents that   fabah-v
best preserve the forms of cells are-                            I onse
Chromic acid.                                         accork
Osmic acid.
Picric acid.                                          RIIliCO
Gold chloride.
The truest appearances are in most cases obtained by              f
chromic or osmic acid; osmic acid will probably be preferred        lotl
in the case of small organisms or portions of tissue on           CeCh
account of the great rapidity and energy of its action; but it
has the great defect of possessing a very feeble penetrating      81eh
power. Pieric acid has very great penetrating power, and          rceiCO
gives excellent results, but requires time for its removal from   imph1;
the tissues. Gold chloride is uncontrollable in its action.        Eiltl
For these and other reasons it will often be advisable to       hath
select one of the remaining reagents. One-third alcohol is         ec
somewhat feeble in its action, but is, on the whole, an            p
admirable reagent for fixing, and has the great advantage of      atI
being the pleasantest of all to work with. Silver nitrate is
useful for the study of superficial structures (epithelia), and
nitric acid and corrosive sublimate are found to give admirable

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