156 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Careful study and experimentation with the different dyes have led to 
the compounding of stains which have enabled the Microscope to reveal 
many of the mysteries of histology and pathology. The introduction of 
the anilin dyes and their successful employment by Koch, led to the 
discovery of the bacillus of tuberculosis, although the existence of this 
organism had been prophesied by writers years before its discovery. 
Golgi’s silver nitrate method has advanced our knowledge of the 
ganglion cells of the cortex of the brain, and perhaps at some day the 
mystery of their poles may be revealed through some simple method of 
staining. The importance, therefore, of the methods of staining is not 
to be overlooked or undervalued in the microscopical examination of 
tissues, and their successful employment may lead to the discovery of 
new facts and data of inestimable value in advancing the present status 
of our science. 
Among some of the recent methods employed in neuro-histology 
and neuro-pathology, perhaps none are so important and satisfactory 
as the Weigert method and the Pal modification of this method. Both 
methods are restricted to the examination of nerve-tissues, more 
especially of the central nervous system, where the gradation between 
white and grey matter is distinct and prominent. 
Both methods require hardening in Miillor’s fluid, or simply in a 
saturated solution of potassium bichromate. A recent writer in 
‘ Neurologisches Centralblatt,’ Dr. Minor, of Moscow, finds that if 
sections of the brain and cord are subjected to the action of the positive 
pole in the bichromate solution, hardening will take place in three, four, 
or five days. After dehydrating and decolorizing in alcohol for some 
days, the preparations are ready for the imbedding mass. I have always 
preferred celloidin for imbedding nerve-tissues, and find that it is an 
excellent agent. It is prepared by allowing several sheets of celloidin 
to dissolve in equal parts of sulphuric ether and 99 per cent, alcohol. 
The preparations to be imbedded are placed in 99 per cent, alcohol for 
24 hours, transferred to equal parts of 99 per cent, alcohol and sulphuric 
ether for another 24 hours, then placed for 24 hours in the celloidin 
solution, fastened upon corks, and are then ready for cutting. 
The sections being more or less delicate and very friable, it is 
necessary to protect them during their passage through the various 
stages of the process. For this purpose collodion, photoxylin, or 
dextrin may be used, the modus operandi being as follows: — Allow some 
of the mass to flow over a glass slide, so that a thin film remains ; dry ; 
then transfer the sections on to this prepared slide, and pour some of 
the mass over the sections, allowing all superfluous quantities to drip 
off. After a few moments the slide may be moistened in alcohol, when 
the sections imbedded in collodion can be removed and handled with 
impunity. 
The Weigert method, first described by Prof. Weigert, of Frankfort 
on Main, in ‘ Fortschritte d. Medicin,’ 1884, p. 190, and 1885, p. 236 ; 
also 1 Zeitschrift f. Wissenschaftliche Microscopie,’ 1885, p. 490, and 
1886, p. 480, requires the sections to be placed in an aqueous-saturated 
solution of cuprum acetate diluted with an equal amount of water for 
24 hours, in a brood oven, or 48 hours in the open air. They are then 
washed in 60 per cent, alcohol a few hours and placed in the Weigert 
