420 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
6een after tlie action of a 1 per cent, aqueous sublimate solution and in 
picric acid preparations. 
After hardening in picric acid, subsequently washed out, the cortical 
layer may be seen as a very fine network, an unnatural condition, the 
result of the formation of vacuoles. In sublimate preparations the 
medullary substance is bestudded with dark granules, while in picric acid 
preparations it is quite clear, and has the appearance of a hollow 
space. The nucleoli in the cells of adult animals usually stain blue 
(cyanophilous), while in the larval condition a few are to be found which 
stain red (erythrophilous). In the early days of larval life there is a 
single large nucleolus composed of both substances. 
New Characteristics of Nerve-cells.* — Sig. G. Magini, who states 
that the absence of chromatin in the nucleus is a special characteristic 
of nerve-cells, as compared with neuroglia-cells, advises for the study of 
this distinguishing feature methylen-blue, and also, but less effectively, 
vesuvin and Ehrlich’s hmmatoxylin. Carmine staining is quite useless 
for the purpose. The objects must be hardened in Kleinenberg’s fluid, 
or in absolute alcohol, or in sublimate. Muller’s fluid is not at all 
suitable. 
Impregnation of the Central Nervous System with Mercurial 
Salts. | — Mr. W. H. Cox finds that a uniform impregnation of the 
central nervous system is obtained when the hardening and impregnating 
fluids are allowed to act together for two or three months. The reaction 
of the hardening fluid should be as slightly acid as possible. The fluid 
which Mr. Cox used consisted of 20 parts of 5 per cent, bichromate of 
potash, 20 parts of 5 per cent, sublimate, 16 parts of 5 per cent, chromate 
of potash, 30-40 parts of distilled water. The preparations cannot be 
preserved under a cover-glass in Canada balsam or dammar, for the acidity 
of the medium and some other unknown cause spoil them. A freezing 
microtome must be used, for the alcohol involved in the paraffin or 
celloidin methods endangers the impregnation. The sections are placed 
for an hour or two in 5 per cent, solution of sodium carbonate, are 
washed in water, placed for a short time in absolute alcohol, then in 
some oil, and finally covered with some rapidly drying resin. If 
they must be covered with a glass, the resinous layer should be allowed 
to dry, and then covered with castor-oil. Then the cover-glass is put 
on and pressed down so as to squeeze out the superfluous oil, or by 
using sty rax, or a mixture of gum-arabic and water, &c., the preparations 
may be kept intact under a cover-glass. 
Preparing Nervous Tissue of Amphibia. f — Mr. A. Smirnow adopted 
the methylen-blue injection method for demonstrating nerve-cells of 
Amphibia. 1/4 to 4 per cent, methylen-blue solutions in 1/2 per cent, 
salt solution were employed. In from half to three hours after injection 
the tissues were removed from the animal, and the stain fixed with 
iodopotassic iodide or picrocarmine or picrate of ammonia. The prepa- 
* Atti R. Accad. Lincei Roma — Rendiconti, vi. (1890) pp. 19-23. See Zeitsclir. 
f. Wiss. Mikr., vii. (1891) p. 519. 
t Arch. f. Mikr. Anat., xxxvii. (1891) pp. 16-21 (1 pi.). 
t Op. cit., xxxv. (1890) pp. 407-24 (2 pis.). See Zeitsclir. f. Wiss. Mikr., vii. 
(1891) p. 511. 
