542 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
surface views and for sectioning, is given in Whitman’s ‘Methods in 
Microscopical Anatomy aud Embryology’ (p. 166). 
With slight modifications, the method is as follows: — 
(1) Break the shell by a sharp rap of the scissors at the broad end ; 
then carefully break away the shell, beginning at the place of fracture 
and working over the upper third or half. 
(2) After removing as much of the white as possible without injury 
to the blastoderm, carefully turn the yolk into a dish of nitric acid (10 
per cent.) deep enough to float the yolk, taking care to have the blastoderm 
on the under side of the yolk. 
(3) The coagulated white should next be removed from the blastoderm 
by the aid of a brush or feather, and the egg then allowed to remain in 
the acid from 20 to 30 miuutes. 
(4) Cut around the blastoderm with sharp-pointed scissors, taking 
care to cut quickly and steadily. After carrying the incision completely 
round, float the blastoderm into a watch-glass, keeping it right* side up 
and flat. 
(5) Remove the vitelline membrane by the aid of dissecting forceps 
and the yolk by gently shaking the watch-glass and by occasional use of 
a needle.f The yolk can sometimes best be washed off by means of a 
pipette. 
(6) Wash in water (several times changed). 
(7) Colour deeply with carmine or haematoxylin. 
(8) Remove excess of colour by soaking a few minutes in a mixture of 
water and glycerin in equal parts, to which a few drops (about 1 per 
cent.) of hydrochloric acid have been added. 
(9) Wash and treat 30 minutes with a mixture of alcohol (70 per cent.) 
2 parts ; water, 1 part ; glycerin, 1 part. 
(10) Transfer to pure 70 per cent, alcohol, then to absolute alcohol 
(95 per cent, alcohol answers every purpose), clarify with creasote or 
clove oil, and mount in balsam. 
For sectioning, blastoderms prepared by this method should be 
dehydrated, either before or after staining, as is thought best, and 
immediately transferred to a thin solution of collodion + (2 per cent.), 
after which they are placed in a thick solution of collodion (5 per cent.) 
and then arranged for imbedding and sectioning. To accomplish this, 
the following procedure has been found useful :• — 
With a camel's-hair brush transfer the blastoderm from 95 per cent, 
alcohol to a paper box. It is better to fill this box partly full of alcohol 
(95 per cent.) before transferring the blastoderm to it, as the alcohol 
partially floats the blastoderm and thus facilitates its removal from the 
brush. As soon as the blastoderm is safely in the box, remove the 
alcohol with a dropper (do not try to pour it off, otherwise the blastoderm 
will curl up), and carefully pour in enough thin collodion to cover the 
* We find it more convenient to remove the yolk from the blastoderm when it is 
kept ventral (or wrong) side up. 
t We find that a small camel’s-hair brush is the best thing with which to 
remove the yolk. 
X We have found collodion more satisfactory, on the whole, than celloidin, and it 
is less costly. To make a 2 per cent, solution, dissolve 2 grams of gun-cotton in 
100 ccm. of sulphuric ether and 95 per cent, alcohol, equal parts of each. For a 
5 per cent solution use 5 grams of gun-cotton instead of 2. 
