712 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The preparations may be contrast stained with eosin in aqueous 
solution. In this case the cover-glasses are first stained with eosin and 
afterwards with methylen-blue, and finally mounted dry or in balsam. 
The eosin stains the red corpuscles pink, the parasites are pale-blue, and 
the nuclei of the leucocytes dark blue. Besides methylen-blue the author 
also used gentian- violet and dahlia, but the results were not so happy. 
Preparing and Staining Blood-films for Examination of Leuco- 
cytes.* — The method adopted by Mdlle. C. Everard, MM. J. Demoor 
and J. Massart for examining the condition of the blood, and especially 
the modification of the leucocytes therein, was as follows : — The blood 
was obtained by puncturing a small superficial vein of the animal’s ear. 
Very thin films were then spread on cover-glasses and fixed with heat. 
The cover-glasses were then laid on a metal plate and heated for an 
hour at 65°-70°. Such preparations, which would keep quite a long 
time, were stained by immersing them for 5-10 minutes in a mixture of 
equal parts of the following liquids : — (1) Eosin 1 grm., alcohol 25 grm., 
water 75 grm., glycerin 50 grm. ; (2) Haematoxylin 1 grm., alcohol 
10 grm., alum 20 grm., water 200 grm. The alum is dissolved by aid 
of heat in the water, and the solution filtered when cold. Twenty-four 
hours after, the alum solution is added to the alcoholic solution of 
haematoxylin, and the mixture filtered after standing for eight days. 
The stained preparation, having been carefully washed in water, is 
passed through 90 per cent, alcohol, absolute alcohol, oil of cloves, and 
mounted in balsam. By this method the nuclei are stained by the 
haematoxylin, while the eosin colours the “protoplasmic granulations.” 
The authors also employed orange, acid fuchsin, and methyl-green, but 
found that the first method was by far the most effective. 
Mode of Investigating Retina of Vertebrates.! — Prof. S. Ramon 
y Cajal finds that the most satisfactory method of studying the retina 
is the rapid method with chromate of silver, already used by Tartuferi. 
As a general rule, he has employed methylen-blue to control the facts 
revealed by the method of Golgi; it can, also, give, as Dogiel has 
shown, very brilliant and quite new results. At the same time it is to 
be noted that methylen-blue does not stain either the fibres of the rods 
and cones or their lower swellings ; nor does it impregnate the fibres of 
Muller, the centrifugal nervous prolongations, or several varieties of 
ganglionic cells or spongioblasts. The transparency is imperfect when 
the retina is fixed with picrate of ammonia, or the mixture of this 
reagent and osmic acid which is recommended by Dogiel. The only 
departures from Dogiel’s method of applying methylen-blue are that the 
retina is stained in situ, and that the fixing reagent is allowed to act only 
for two instead of for twenty-four hours. 
Apathy’s preservative fluid — a syrupy solution of gum arabic and 
sugar, has been found satisfactory. The valuable rapid method of Golgi 
does not always act in the same way on the small retinae of Fishes, 
Batrachians or Reptiles ; in fact, the more delicate the retina, the more 
difficult is it to impregnate it well. For example, more satisfactory pre- 
parations are obtained with the eyes of Lacerta viridis than of L. agilis. 
For small eyes a method of double impregnation is recommended : the 
* Ann. Inst. Pasteur, vii. (1893) pp. 166-7. 
t La Cellule, ix. (1893) pp. 126-31. 
