AND OF HYBRID PIGEONS. 
5 
then transferred to cedar oil or xylol. Too prolonged immer¬ 
sion in clove oil seems to extract the gentian violet. 
A reagent which is unsurpassed for the study of the individ¬ 
ual chromosomes, the spindle and the centrosomes, is Gilson’s 
mercuro-nitric fixing mixture, followed by iron-haematoxylin 
for staining. After such treatment, the chromosomes come out 
as clear cut as if stamped with a die. Tissues are cut into small 
pieces and left in the fluid from 4 to 6 hours. They are then 
washed thoroughly in 50% alcohol. Satisfactory preparations 
can be obtained only with thin sections measuring from 3 to 5 
micra in thickness. To get the best results, the sections should 
be treated with the iron-alum for about 8 hours and then left 
for 36 hours in haematoxylin. After washing in water, they 
should be almost completely decolorized in the iron alum (15 
to 30 min.). Thus, the haematoxylin is left in the chromatin 
only. The color of the haematoxylin may be deepened by a 
short immersion in a slightly alkaline solution before treatment 
with the plasma stains. Of the latter, either Bordeaux red or 
orange G. gives good results. To see the centrosomes to the 
best advantage the decolorization should not be carried so far. 
Among other valuable fluids should be mentioned that rec¬ 
ommended by Lenhossek^ in his paper on the spermatogenesis 
of the rat. The formula is as follows: 
Platinum chloride 1% =50 cm. 
Sat. sol. cor. sub = 50 cm. 
Glacial acetic = 5 cm. 
This gives a more faithful preservation of the cell cytoplasm 
and of the interstitial cells than Gilson does. It may be fol- 
lov/ed by almost any of the common stains. The iron-haemato¬ 
xylin method gives very satisfactory results, as does also cyanin 
and erythrosin, or majenta followed by picric acid. This killing 
reagent has proved itself an excellent one also for general cyto- 
logical work, especially in splanchnological research. For 
general purposes, according to Mr. A. D. Dunn, %% platinic 
chloride may be substituted for the 1%, thus considerably 
reducing the cost of the fluid without materially interfering with 
its efficacy. 
1. Lienhossek, M. v: “Untersuchungen ueber Spermatogenese.” Arch. f. 
mikr. Anat. LI., 1898. 
