174 SUMMARY OF CURRENT RESEARCHES RELATING TO 
in the heavy foot of the instrument ; the knife is fixed to the foot in a 
vertical position. The small side-movement of the object is effected by 
a micrometer screw and toothed wheel carried within the rectangular 
frame. 
2. For Celloidin-Imbeddings and for Cutting in Liquids . — Here the 
knife is carried horizontally on a rectangular frame, which, in this in- 
strument, works about a vertical axis ; the object is fixed to the foot of 
the instrument, and the small movement is given to the knife by the 
micrometer arrangement within the rectangular frame. For cutting in 
liquids, a small bath is arranged round the object-holder, and the knife 
is carried on an arm bent twice at right angles and projecting over the 
edge of the bath. 
Manipulation of Celloidin Sections.*— By the following procedure, 
devised by Dr. G. Aubertin, the chief inconveniences inherent in the 
ceiloidin-section may be avoided. The sections, cut in 70 per cent, 
alcohol, are arranged on the slide. The celloidin is then dehydrated, 
first in 70 per cent., and finally in absolute alcohol. When perfectly de- 
hydrated, the celloidin is dissolved by dropping on very carefully a mix- 
ture of ether and alcohol in equal parts, with which the whole surface of 
the slide should be just covered. The ether-alcohol mixture may be re- 
newed until the whole slide is covered with a very thin layer of celloidin. 
The ether-alcohol is allowed to evaporate, but not to complete dryness 
of the celloidin. The membrane thus formed is not only firm, but 
so delicate that staining is easily effected. The after-treatment sug- 
gested is — 70 per cent, alcohol, water (20 minutes), dilute solution of 
borax-carmine (some hours), water (10 minutes), haematoxylin (10 minutes), 
hydrochloric acid-alcohol until the celloidin is decolorised. The pre- 
parations should be dehydrated in 95 per cent, spirit, cleared up in 
xylol-carbolic acid (3-1), and mounted in balsam. 
(4) Staining- and Injecting. 
Investigation of Brain of Fishes.f — M. Catois has made use of a 
process which he describes as a combination of the injection-methods of 
Ehrlich and Meyer with the immersion-method of Dogiel, and the diffu- 
sion-process of Cajal. 
Into the living animal there were injected 1 to 2 ccm. of concentrated 
salt solution of methylen-blue ; on the brain being removed, sections 
were made of it, and the pieces placed for about half an hour in a 
saturated solution of methylen-blue, after which they were treated in 
the ordinary way. 
Preparation of Embryonic Nervous System of Crustacea.! — M. N. 
de Zograf has made use of Prof. Ramon y Cajal’s method of double 
impregnation ; he reports that he had many difficulties to overcome 
before succeeding with the larvae of Copepoda. He could not cover the 
Nauplius with a layer of glycerin and gelatin to .preserve it from the 
silver precipitate, as is often done with minute objects, for this reagent 
dehydrates the larvae, and makes it impossible to recognise their struc- 
* Anat. Anzeig., xiii. (1897) pp. 90-3. 
f Comptes Rendus, cxxiv. (1897) pp. 204-5. J Tom. cit., p. 202. 
