122 
PRACTICAL PHOTO-MICROGRAPI-IY. 
out on the plate the danger of fog from unsafe light is 
considerably less than before development. The plate 
is laid him upwards in the developing dish, and the 
solution is swept over the him, so that all parts of the 
him are wetted at once, or as nearly so as possible. 
The plate should be kept rocking, more or less, during 
the operation ; if this is neglected there is danger of 
uneven markings appearing on the plate. 
Experience alone will teach when to stop develop¬ 
ment ; some plates require to be carried further than 
others ; some subjects require the negatives to be made 
denser than others. But when the development is 
complete, the image, looked through , appears very much 
too dense. Details may or may not show on the back 
of the plates ; as a rule they do show. It is always 
safe to err on the side of full development; for if the 
plate is too dense it is easy to “ reduce ” the density as 
explained on page 128. But there are few occasions, 
as, for instance, when a preparation is much wanting 
in contrast of actinicity—as poorly stained or bacteria 
preparations—when it will be better not to over-develop, 
but rather to get detail without much density, and 
without reduction of silver in the image of the critical 
bodies themselves, and to trust to further operations, 
such as intensification (page 129). 
When a plate is fully developed the image looked at 
is practically a black or very dark grey expanse of him 
with little more than a suggestion of differentiation in 
the details. The plate is then washed for a minute 
under the rose tap, and placed directly in the fixing 
