452 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
treat them with eau de Javelle and, having soaked them in glycerin, 
mount in glycerin or glycerin jelly. For stained and permanent pre- 
parations, the sections, after removal from eau de Javelle, should be 
neutralised by means of an aqueous 5 per cent, solution of sodium 
sulphite, and the sulphite eliminated with water mixed either with 
alcohol or glycerin. The sections may then be stained in an aqueous or 
alcoholic 'solution, and, having been dehydrated in alcohol, mounted 
in balsam. The various steps in the manipulation should be carried 
out in cylindrical vessels which will allow the slides, placed back to 
back, to stand upright. The various stages require several hours 
apiece, owing to the slowness with which the agar parts with the previous 
reagent. This is really the great inconvenience of the agar fixative. 
(6) Miscellaneous. 
Bichromates and the Nucleus.* — Dr. E. Burchardt has made a de- 
tailed study of the diverse influence of bichromates on the nucleus. One 
set of salts destroy the nuclear structure, namely salts of potassium, 
caesium, rubidium, sodium, lithium, ammonium, magnesium, strontium, 
and zinc. Another set of salts preserve the nuclear structure, namely 
salts of calcium, barium, and (to a less extent) copper. What is pre- 
served is usually the chromatin, not the achromatin portion of the 
nucleus. All bichromates, however, seem to have two mutually an- 
tagonistic effects on the formed and unformed constituents of the 
nucleus. According to the predominance of one or the other effect, and 
according to the state of the fluid nuclear sap, there is destruction or 
preservation of nuclear structure, or something between the two states. 
The zinc salt seems in its effects about midway in the series, with sodium, 
ammonium, potassium, *&c., on the one side, copper, calcium, and barium 
on the other. 
Method of Graphic Reconstruction from Serial Sections.f — Mr. W. 
McM. Woodworth describes a method of reconstructing from serial 
sections by means of measurements made with an ocular micrometer 
directly from the sections themselves, without the aid of camera lucida 
outlines ; and as the measurements can be multiplied to any extent, re- 
constructions to any scale can be produced with any combination of 
objective and ocular. The method, however, is practically limited to 
transverse sections of bilaterally symmetrical objects, though it can be 
applied to objects of any shape or outline if they can be provided with a 
plane of definition at right angles to the plane of section. The example 
given is the reconstruction on a frontal plane of the intestinal canal of 
a small Trematode at a magnification of 100 diameters. The worm is 
2 mm. long, and the sections are 20 p thick. The latter are measured 
with a Zeiss AA objective and ocular micrometer 3, at a tube-length of 
16 mm. Under these conditions the value of one division of the micro- 
meter is 17*2 p. On a sheet of paper draw a line 200 mm. long to re- 
present the chief axis of the worm one hundred times enlarged, and at 
right angles to this draw 100 parallel lines at intervals of 2 mm. 
* La Cellule, xii. (1897) pp. 337-73.' 
t Zeitsckr. f. wiss. Mikr., xiv. (1897) pp. 15-8. 
