184 



Specific Examples of Slide Making 





132 



Figs. 132, 133, and 134. Chick embryo prepared by the method described in this 

 example. Fig. 132. An excellent slide. Fig. 133. A good slide ruined by the application 

 of a dirty coverslip. Note dust granules at 1 and 2. Fig. 134. A complete failure. The 

 wrinkles at 3 show that the embryo was not properly attached to filter paper before 

 fixing. The drawn-out diffuse myotomes at 4 and the absence of head development 

 indicate that the embryo had died some time before fixation. The crack in the dark 

 background at 5 indicates that the yolk was imperfectly removed before fixation. 



end of the egg and to let the air bubble out through the warm saline 

 solution. This permits the yolk to fall down out of contact with the upper 

 surface of the shell, which may be removed with blunt-nosed forceps, 

 working from the air space toward the center. Again the matter of practice 

 is involved, for a skilled operator can remove this shell in large portions, 

 whereas the inexperienced must work very carefully to avoid puncturing 

 the yolk. If the yolk is punctured, it is much simpler to throw the egg 

 away and start with another one. After about half the shell has been 

 removed, it will be found relatively easy to tip the yolk, with the embryo 

 lying on top of it, out into the saline solution and remove the shell. 



The next operation is to cut the embryo from the yolk by a series of cuts 

 made well outside the terminal blood vessel, which marks the limits of 

 the developing embryonic structures. To do this with success requires 

 more courage than experience. Just as soon as the vitelline membrane is 

 punctured, the yolk starts squirting out through the hole, rendering the 

 fluid milky so that one can no longer see the embryo. The smaller the hole 

 cut, the more violently does the yolk squirt out, so the larger the scissors 



