538 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
a mordant. After having been washed they are placed in the logwood 
solution for about twenty hours. The overstaining is removed by 
decolorizing with Weigert’s borax and ferrocyanide of potash solution. 
The proper degree of differentiation is attained when the rod and cone 
layer alone remains of a dark colour, the rest of the layers having a 
brownish hue to the naked eye. The sections are then washed in water 
and mounted in balsam in the usual manner. 
Haematoxylin as a means for ascertaining the Alkalinity or Acidity 
of Tissues.* — Prof. F. Sanfelice has found that the acid or alkaline 
reaction of tissues may be recognized by staining with Boehmer’s 
haematoxylin (alkaline), or with the author’s iodized haematoxylin (acid).f 
In using this method as a test, two principal precautions must be 
observed. First it is necessary that the normal reaction of the tissue 
must not be interfered with, hence reagents such as chromic acid and 
its salts, Muller’s fluid and Flemming’s solution are unsuitable fixatives. 
The author used chiefly absolute alcohol for hardening and fixing, and 
also corrosive sublimate, the excess of which must always be carefully 
extracted with spirit. The second precaution is that the haematoxylin 
solution must have only a feeble reaction. 
Among the instances of differential staining obtained by this method 
it is mentioned by the author that the protoplasm masses in the ovary and 
testicle of Selachians are coloured red when the whole of the tissue is 
treated with the alkaline solution — a fact which proves that the ele- 
ments undergoing this form of necrobiosis acquire an acid reaction. 
Goblet-cells in the intestinal mucosa become coloured blue, while the 
rest of the tissue remains red. Hence the reaction of goblet-cells is 
alkaline, and this method might be usefully employed to ascertain the 
reaction of tissues or elements, and their products. 
New Method of Staining Central Nervous System, and its 
Results.! — Prof. P. Flechsig recommends the following method for 
staining the nerve-cells of the cerebral cortex and their prolongations. By 
means of it it was shown that the axis-cylinder process was the only 
prolongation from the cell which was in connection with a nerve-fibre ; 
that the axis-process, which is not at its commencement medullated, 
divides like a T, i. e. dichotomously at a right angle. In the occipital lobe 
a trichotomous subdivision was the rule, although frequent subdivision 
was also remarked. In the neighbourhood of the central fissure some 
axis-fibres d:d not subdivide. 
These results were obtained by hardening pieces in 2 per cent, 
aqueous solution of chromate of potash, and then making sections not 
exceeding 5/100 mm. in thickness. 
After soaking in 96 per cent, spirit, the sections are kept for 
3-8 days in a solution of redwood extract at a temperature of 35° C. 
The sections having been washed in distilled water are then decolorized 
in the following manner: — Each section is placed in 3 ccm. 1/4-1/5 per 
cent, solution of permanganate of potash until the solution have lost its 
* Journ. de Micrographie, xiv. (1890) pp. 21-2. 
f See this Journal, 1889, p. 837. 
i Berichte ii. d. Verhandl. K. Sachs. Gesell. Wiss. Leipzig, 1890, pp. 328-30 
(1 pi.). 
