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8UMMARY OF CURRENT RESEARCHES RELATING TO 
Orthochromatic Sensitiveness . — Though commercial orthocliromatic 
plates are sensitive for the green and red, and generally give satis- 
faction, M. Monpillard says that, for scientific purposes, he prefers 
ready orthochromatized plates, which, when used shortly after prepara- 
tion, have a maximum of sensitiveness to the luminous radiations. The 
operation of orthochromatization demands only elementary care. The 
dark-room lamp should have two thicknesses of deep ruby glass, 
the flame being reduced to as small a degree as convenient during the 
bathing of the plates. After the plates are bathed they are passed 
through three dishes of distilled water, and are finally dried in a drying 
cupboard containing a vessel in which calcium chloride is placed. 
For photomicrographic purposes the following colours give the best 
results : — (1) Erythrosin (for green-yellow, yellow, and yellow-orange) ; 
(2) Cyanine (for red-orange and red). 
M. Monpillard says the following formulas have given him satis- 
faction : — 
Erythrosine (stock solution) : — Erythrosine 1 part ; distilled water 
1000 parts. 
Sensitizing bath : — Stock solution of erythrosine 4 ccm. ; water 
100 ccm. ; ammonia, 0*5 ccm. 
Cyanine (stock solution): — Cyanine 0 • 1 part ; alcohol (95 percent.) 
100 parts. Only a small quantity of the solution should be prepared and 
it should be kept in the dark. 
Sensitizing bath : — Stock solution of cyanine 4 ccm. ; water 100 
ccm.; alcohol (95 per cent.) 5 ccm.; ammonia 1*5 ccm. The plates 
are immersed in either of the foregoing baths for two minutes, and are 
then washed and dried as directed. 
Erythrosine and cyanine plates bathed in both erythrosine and 
cyanine are rendered sensitive to yellow and red. The first bath con- 
sists of : — Stock solution of erythrosine 20 ccm. ; distilled water 80 ccm. 
After two minutes’ immersion the plates are washed in two waters, and 
are then bathed in the cyanine solution given, washed and dried. 
Plates so treated are, it is pointed out, very much slower, but this 
is no disadvantage in photomicrography, and, on the other hand, they 
do not fog in development, which frequently happens when, to raise their 
general sensitiveness, the orthochromatizing bath is preceded by an 
alkaline bath. 
Coloured Screens. — Coloured screens may be used either in the form 
of stained collodion, or, preferably, a small glass trough with parallel 
faces may be fitted with either of the following solutions : — 
(1) For light-yellow screen : — Neutral chromate of potash 1 grm. ; 
water 100 parts. 
(2) For deep-yellow screen : — Neutral chromate of potash 5 grm. ; 
water 100 parts. 
(3) For orange screen : — Bichromate of potash 8 grm. ; water 
100 parts. 
(4) For red screen : — Erythrosine 0*2 grm. ; water 100 parts. 
No. 1 weakens the blues and yellows ; No. 2 extinguishes them ; 
No. 3 cuts off the blue ; No. 4 accentuates the action of the red. 
With those coloured screens, and having sensitized the plates for 
given colours, it will bo easy to obtain in their true values reproductions 
