356 
AERIGO VISENTINI. 
The cultures were always very rich in parasites and of 
very recent date (from two or three days to a week), in order 
to avoid the presence of dead or altered forms and to obtain 
the greatest possible number of dividing forms. 
It is an essential precept to fix the preparation imme- 
diately, before the smear dries, because, as in the case of 
very many other Protozoa, the Leishmanias become deformed 
rapidly, assuming always a form more stumpy or even 
rounded ; the method of drying, besides itself altering the 
form and the structure, is not a sufficiently rapid means 
of fixation. It is for this reason that those authors who have 
made use only of dried smears, stained with Giemsa’s stain, 
have given incomplete and inexact descriptions, as recently 
Franchiui. In particular, with this method the rhizoplast is 
not always successfully demonstrated, and never the exact 
connection of the latter with the kinetonucleus. 
For fixation I have made use largely of Schaudinn’s 
alcoholic sublimate and of Maier’s fluid, which is a slight 
modificatioti of the former ; of osmic acid, followed by subse- 
quent fixation in methyl alcohol, absolute alcohol, or 
Schaudinu’s fluid; and of Flemming’s fluid and Hermann’s 
fluid, always used cold. After fixation in mixtures containing 
sublimate, I have followed usually the technique indicated 
by Giemsa for wet smears and sections, that is to say, treat- 
ment with iodine solution and afterwards with hyposulphite; 
but I abandoned this procedure when, like Rosenbusch, using 
a solution of sublimate in which there were no crystals, I 
made the fixation last but a short time. 
Two methods of staining have given me especially good 
results — Giemsa’s method for wet smears and Heidenhain’s 
classic iron-haematoxylin ; I have not had equally good 
differentiation of the stain with the abbreviated procedure of 
Rosenbusch, which, however, gives good results and has 
the advantage of saving much time. The differentiation of 
the preparations is especially delicate and difficult, requiring 
to be checked by frequent examination under the microscope ; 
for this purpose I have made use with advantage of the water- 
