I879-J 
Notes . 
705 
hardening protoplasmic structures with the minimum of shrink- 
age, and also staining fat of an intense black colour. The 
former property renders it of great value in embryology and in 
the study of infusoriae and delicate animal tissues : the latter 
gives it its pre-eminence in bringingout the ramifications of the 
finer medullated nerves, and the structure of the adipose tissue. 
Some recently-hatched glass-crab (Phyllosoma) were immersed 
for ten minutes in a 1 per cent solution of osmic acid, and sub- 
sequently treated with alcohol of gradually-increasing strength, 
commencing with 50 per cent, and ending with absolute. The 
central nervous mass was stained jet black ; the muscles, 
glands, &c., assumed a greyish brown, the striae of the muscular 
fibres becoming remarkably distinct. It has been used with 
great success for the preparation of delicate vegetable tissues ; 
the manipulation is similar, after staining and treatment with 
alcohol ; soaking in oil of cloves follows ; the sections are cut 
by imbedding in cocoa butter, and mounted in balsam. A mix- 
ture of osmic and chromic acids (chromic acid, 0^25 per cent, 9 
parts; osmic acid, 1 per cent, 1 part) answers, in some respects, 
better even than osmic alone for vegetable preparations. 
In the same journal (vol. II. p. 354) is a paper by George 
Hoggan, M.B., and Frances Elizabeth Hoggan, M.D., “ On the 
Development and Retrogression of the Fat Cell.” The mode of 
preparation of the specimens is minutely described, and the 
manipulation and effect of the various staining and other 
reagents given in detail. 
The employment of osmic acid and other stains is opening 
a new field for the histologist. The following process is used 
by Dr. Richard Altmann, of Giessen, for the investigation of 
certain animal tissues under the microscope : — The tissue is 
either impregnated by soaking, or else its vessels are injected 
with olive or castor oil, and then placed in osmic acid until the 
oil is hardened and blackened ; finally it is transferred to a solu- 
tion of potassium or sodium hypochlorite (“ Eau de Javelle”), 
which completely destroys the tissue, the fatty material being 
left, and retaining the form of the vessels or spaces into which 
it was injected. The solution of osmic acid is of 1 per cent 
strength. The process has been successfully employed for the 
investigation of medullated nerve, striped muscle, epithelium, 
cornea, choroid, and retina. Full details will be found in the 
“ Archiv fur Mikroskopishe Anatomie.” vol. xvi. (1879), p. 
471 ; a translation in the “ Journal of the Royal Microscopical 
Society ” for August. The Royal Microscopical Society are 
doing good service by the carefully-selected translations of foreign 
papers on biological subjects. 
Chemistry and Technology. 
It would seem that restrictions upon the Chemical Arts, to 
whatever length they may be carried, must fail to prevent the 
