154 THE AMERICAN MONTHLY [ August, 
tion and stability ; its disadvantages bring coloration of the tissue, brittleness 
when used too long’ or too strong, and an almost absolute exclusion of the 
ordinary carmine and hematoxylin stainings. We have usually fixed the 
fresh tissue (in small pieces) in a comparative strong solution (1%) for 8 to 
12 hours; washed in running water for several hours, and hardened in 50, 
So alcohol. The elements of tissues so treated will generally be found to be 
very satisfactorily preserved in form and structure. 
Where an accurate and especial examination of the cells chiefly concerns 
the investigator, as in studying spermatogenesis, etc., the later solution of 
Flemming is the general favorite; this later mixture, it will be remembered, 
is much stronger than its predecessor, consisting of chromic acid (1%) 7 
parts, osmic acid (2%) 2 parts, glacial acetic acid 4 to1 part. In this mix- 
turethe absolutely fresh tissue is allowed to remain at least 24 hours, in 
many cases with advantage for 2 or3 times as long ; thorough washing for 1-2 
hours, and hardening in 70, 90, and roo alcohol follow. Success with 
Flemming’s solution requires two precautions :—freshly mixed solution, and 
sufficiently thin (2-3 mm.) pieces of tissue. Where pieces too thick are 
used, the centre will be found to have been effected by the chromic acid 
alone, as the action of the osmic acid is confined to a limited external zone. 
Let it be emphasized that fresh tissues are never to be subjected to the action 
of water before being fixed; and that for the investigation of delicate cells, 
the tissue must be taken from the sas¢ killed animal and a¢ once transferred 
to the fixing reagent—that the tissue still warm (which in large organs may 
be the case after some considerable time) is no guarantee that the ce//s have 
not undergone change. 
While the excellence of these chromic acid solutions is generally admitted, 
yet the great difficulty of obtaining good hematoxylin stainings, and the abso- 
lute impracticability of using carmine, deters many from generally employing 
these fixing fluids. Saffranin is very useful for displaying nuclear figures in 
tissues so treated, yet such preparations leave much to be desired where the 
remaining parts of the cells are to be studied. A decided advance, it seems 
to us, is offered with the hematoxylin of Delafield, by which admirable 
preparations may be obtained. Attention may be called, however, to Benda’s 
modified copper-hematoxylin, of the excellence of which nearly a year’s con- 
tant use has thoroughly convinced us. Admitting that the method is some- 
what troublesome, the results amply repay where a careful study of cells 
under high powers is proposed. 
Tissues treated with chromic acid or Flemming’s solution stain readily, 
as well as do those hardened in alcohol or any other of the usual fluids. 
For careful examination staining after cutting is to be recommended. The 
sections on the slide or cover are placed for 8-12 hours in an almost satu- 
rated solution of cupric acetate (to which a few drops of acetic acid may be 
added) in the oven at 50° C; washed a few minutes in two changes of dis- 
tilled water, and stained with 1o% alcoholic solution of hamatoxylin until 
very dark blue; transferred dérect/y to hydrochloric acid solution (1: 350), 
where they remain until bleached to a straw tint ; after being rinsed in water, 
they are placed in fresh copper solution until again blue, care being taken to 
stop the reaction (by transferring to water) before the trssue becomes too 
dark, as the tint will be somewhat deeper after the final washing (which 
must be thorough) and dehydration. Should the sections be too dark, they 
may be again bleached in the acid, and passed through the copper solution 
as before ; should they be too pale, they may be once more placed in the he- 
matoxylin, and carried through the solutions as at first. The advantages of 
the method are certainty of good results after chromic acid, control of the 
intensity and ease of correcting faults of the stain, and, above all, the excel- 
