134 
SUM M An* OF CURRENT RESEARCHES RELATING TO 
has turned brown it is transferred to distilled water, in order to remove 
excess of osmic acid, and then teasing out is resumed in a 2 per cent, 
solution of silver nitrate. The nerve-bundle is exposed to light for 20, 
30, or 40 minutes, and must be occasionally moved about. The excess 
of silver nitrate is removed in distilled water and the preparation mounted 
in glycerin. 
Impregnation is much facilitated if the nerve-fibres are treated with 
an aqueous 1 per cent, solution of eosin, neutral carmine or even hsema- 
toxylin before mounting in glycerin. 
By this method the author claims that a series of rings situated at 
the level of the myelin segments can be demonstrated, and from the 
illustrations it would seem that the overlapping of two myelin segments 
is related to the well-known appearance called Ranvier’s node, the cuff 
of the outer myelin tube overlapping the inner segment being the trans- 
verse bar of the Latin cross. 
Cox’s Method for Demonstrating the Nerve-fibres of Central 
Nervous System.* — Prof. S. Ramon y Cajal found that Cox’s method 
gave very satisfactory results when employed for demonstrating nerve- 
fibres in the cornu Ammonis and elsewhere. This procedure consists in 
placing pieces, not too large, in the following fluid : — 5 per cent, 
bichromate of potassium, 20 parts ; 5 per cent, sublimate, 20 parts ; 
distilled water, 30-40 parts ; 8 per cent, chromate of potassium with 
strongly alkaline reaction, 16 parts. In this fluid the pieces remain for 
2-3 months in the winter, and at least one month in the summer. 
Before being imbedded the pieces are immersed in 36° alcohol for 30 to 60 
minutes. The sections are placed in 40° alcohol, cleared up in oil of 
cloves, mounted in xylol-dammar without a cover-glass. 
The author also used the Weigert-Pal and Golgi’s rapid methods, 
and also tried Berkeley’s rapid method (osmic-copper-hsematoxylin), of 
which he speaks very favourably. 
Examining Street Dust for Tubercle Bacilli.f — The examination of 
dust from the street, dwelling-rooms, of dirty water, &c., depends, says 
Dr. Marpmann, for its success on the recognition of those granules into 
■which the bacilli have become disintegrated rather than finding the intact 
organisms. The staining reaction is exactly the same, but the red 
particles require to be sought for with an apochromatic immersion instead 
of with the ordinary 1/12. The dust used for the examination was just 
scraped up and digested for some hours in water at 40° ; it was then 
strained through a woollen cloth. Some of the filtrate, about 50 ccm., 
was then treated with a drop of iron chloride, and 10 drops of carbonate 
of ammonia in solution. A precipitate of iron oxide and earthy car- 
bonates slowly formed, and this was separated either by sedimentation 
for twenty-four hours in a conical glass or by centrifuging. 
The sediment was then stained on cover-glasses with phenol-fuchsin 
treated with hydrochloric acid-alcohol (HC1, 0*5; 80 per cent. C 2 H 6 0, 
100) and examined in fat-blue ( Fettblau ) in xylol. 
It only remained to find out whether these fragments of bacilli were 
infectious, and cultivations were made therefrom in agar tubes and 
* Zeitschr. f. wi6s. Zool., lvi. (1893) pp. 616-8. 
t Centralbl. f. Bakteriol. u. Parasitenk., xiv. (1893) pp. 229-34. 
