EXPERIMENTAL EQUIPMENT AND PROCEDURES 



Secure a 5-lnch piece of 7 nan. soft glass tubing and in a hot flame reduce 

 the diameter of one end to about 1 mm. Then place a right angle in the tube, at 

 ita center (flame tip) and when cool, pass the flamed end through a hole in a 

 large cork. Mount the cork in a burette clamp attached to a ring stand so that 

 the micro-burner is turned upward. To the other end of the tube attach a rubber 

 tubing Joined to the gas outlet. Apply a screw to the rubber tubing. B^ regu- 

 lating the screw clamp a micro-flame of intense heat may be secured. The usual 

 type of micro-burner, where the tube is drawn out to a thin tip of small bore, is 

 not so likely to remain uniform when in use. Hypodermic needles may be used as 

 micro-flame tips. 



2. Glass needles : There are two types of handles used for glass needles. The stan- 

 dard type consists of a 7 mm. diameter glass rod cut into 10 cm. lengths by flam- 

 ing longer pieces in the center and drawing them out. In this manner one end of 

 the rod is tapering. The tapering end should be brought into the flame so that it 

 retracts to knob for attachment of the needle, made separately. See that the knob 

 and rod are perfectly straight. Prepare 10 such needle handles. The second type 

 of needle holder consists of the regulation steel needle holder with adjustable 

 screw into which various needles may be inserted and fastened. This type is con- 

 venient and entirely satisfactory. 



The needles may be made on the electric needle-puller but this is not neces- 

 sary. Secure some h-'^ mm. soft glass rod and in a flame tip draw it out perfectly 

 straight \intil a thickness of about 1 mm. is secured. Break this into about 7-8 

 cm. lengths and in the micro- flame, put a hook or a bend toward the end of each 

 piece. Hang this "hook" over any support (Metal rod) attached to the ring stand 

 in such a manner that it is directly above a 20 x 60 mm. (or larger) glass vial. 

 In the bottom of the vial place a small amount of cotton. 



At about 2 cm. from the base of the hanging glass rod apply the micro-flame 

 from the side. It will take practice to apply the correct amount of heat. When 

 the glass at the point of heat application is melted, the weight of the hanging 

 will drop it into the cotton in the glass vial, providing a needle point of micro- 

 scopic dimensions. With practice it may be possible to do this in two steps, the 

 first heating will lengthen and thin out the rod and the second will draw an even 

 finer point. In any case the tapering micro-point should not be long and flexible 

 and will probably have to be trimmed with sharp scissors. Draw out many such 

 needles at one time and mount them temporarily in plasticene, i.e., until ready to 

 attach them to holders or to mount them in a needle board. These needle points 

 may be attached to the glass handles (described above) by bringing them together 

 in a small flame. The needles may be attached at a slight angle which will facili- 

 tate operations. 



5. Steel needles : The ordinary steel needles are much too coarse for work with small 

 embryos. However, the finest Insect needles may be secured, cut short, and moiuited 

 in wooden handles and will be extremely useful. 



k. Hair loops : This device is for handling embryos or isolated tissues. Draw out 

 the end of some 5-6 mm. soft glass tubing so that the total length is about 10 cm. 

 and the smaller end has a diameter of about 1 mm. Close the larger end in a 

 flame. The smaller end should be cut off with a diamond pencil or flamed to make 

 it smooth. Secure some blonde hair from a newborn infant and cut it into 1 inch 

 lengths. With forceps insert one end of the hair into the capillary opening and 

 then the other end Into the same opening. Eegulate the insertion of the hair so 

 that a relatively small loop protrudes. Melt a small amount of soft paraffin on 

 a glass slide and dip the hair- loop into the paraffin, whereupon some of the par- 

 affin will run up into the tube, and harden upon cooling. This will hold the hair 

 loop in place. To remove ariy paraffin adherent to the hair loop Itself, warm a 

 slide in a flame, place on it a small piece of filter paper, and gently touch the 

 hair-loop to the filter paper. Avoid melting the paraffin within the capillary 

 tube. 



