PROCEEDINGS OF THE SOCIETY. 
769 
staining were resorted to for two purposes — firstly, to aid in tlie investi- 
gation of the structure in its normal conditions, and, secondly, to 
determine wliat changes had taken place in such structure under diseased 
conditions ; many of the methods in use being employed for both 
these purposes. Putting aside from present consideration the old- 
fashioned but extremely good methods of staining with carmine, picro- 
carmine, logwood, &c., as being now little used alone in physiological 
investigations, reference was made to the various anilin stains, all kinds 
of which had been tried with varying success. One of the best known 
and most serviceable of these was Bevan Lewis’ anilin-blue-black method, 
in which fresh sections were placed in a ’25 per cent, aqueous solution 
of the stain, and afterwards washed and developed. Excellent results 
were obtained by this process, of which a good example was shown under 
one of the Microscopes upon the table. Weigert’s method differed entirely 
from this, and by its means many very important pathological facts had 
been brought out. It might briefly be described as hardening by a 
solution of potassium bichromate, and staining by a solution of hsema- 
toxylin, afterwards being washed in water and treated with ferricyanide 
of potassium and borax. For human neuro-pathology this still held the 
field, although for experimental work it had been largely replaced by 
Marchi’s method, where osmic acid was employed in conjunction with 
the potassium bichromate. 
Pal’s modification |of Weigert’s method was, however, mostly used : 
in this, after hardening and staining, the sections were treated with 
permanganate of potash, and then bleached with a solution of potassium 
sulphite and oxalic acid. Its value depended upon the staining reaction 
of the medullated sheath, only the medullated fibres and not the cells 
being permanently stained — the chief principle to be borne in mind 
whilst working with this method being the complete saturation of the 
tissue with the bichromate of potash. In illustration of the results 
obtained by this method a series of sections so treated were shown upon 
the screen by the projection Microscope : (1) Section of normal spinal 
cord of monkey ; (2) Section of same showing degeneration, the diseased 
portion remaining unstained ; (3) Section of human foetal spinal cord ; 
(4) Section of medulla oblongata of monkey, &c. These methods of 
investigation showed the central nervous system to be built up of nerve- 
cells and their processes, the nerve-fibres, and the binding substance 
or neuroglia; previous methods had shown the nerve-cells and fibres 
more or less well, but until quite recently all had failed to show the 
extraordinary formation of cell processes. This recent method was the 
osmium-silver bichromate, or Golgi’s method, originally described by 
Golgi in 1880, although not much known generally until 1889, when 
Ramon-y-Cajal of Barcelona used it, and Kolliker employed it very 
largely and with great success. Since that time it had been much used 
upon the Continent, but had been only adopted in England during recent 
years. The process itself was simple, but somewhat expensive and un- 
certain. The material was first hardened in a solution of bichromate 
of potash and osmic acid, and then put into a solution of silver nitrate ; 
after being washed in water, the sections were dehydrated by alcohol, 
and mounted in Canada balsam without a cover-glass. The principle 
of this method seemed to be the formation of a bichromate of osmium 
