208 



Specific Examples of Slide Making 



mm 



144 



145 



Figs. 144 and 145. Good and bad salivary-gland chromosomes prepared by the 

 method described in this example. Fig. 144 shows well-spread chromosomes with 

 the bands clearly marked. Fig. 145 is the result either of letting the salivary gland 

 dry before applying the stain or of imperfect crushing. The dark background in both 

 pictures is caused by the presence of residual stain and cannot be avoided in prepara- 

 tions of this type. 



left hand and insert the point of the right-hand needle into the center 

 of the mouth parts. With a continuous, steady pull drag the mouth parts, 

 and whatever comes with them, into the drop of Ringer's solution. The 

 salivary glands will now be clearly apparent as two translucent sausage- 

 shaped bodies on each side of the esophagus. Both needles are now used 

 to detach the mouth parts, and as much adherent fat as possible, from 

 the glands. The glands are now pushed onto the point of the right-hand 

 needle, lifted out, and immediately placed in the drop of stain on the 

 second slide. 



As many glands as required are accumulated in the drop of stain and 

 left to soak for at least 5 min before the coverslip is pressed on. 



After the glands have soaked long enough, a large ( %-in. square cover- 

 slip) is pressed on the drop. A sheet of bibulous paper is then pressed on 

 top and the ball of the forefinger rocked backward and forward with a 

 light pressure over the center of the coverslip to force out the excess 

 stain. A clean piece of paper is now pressed over the coverslip and again 



