548 APPENDICES 



ends of each in the flame. Two sterile pipettes with sealed ends are thus formed, 

 as shown at c on the figure. 



2. To make a bulb pipette. — Take a Pasteur pipette as described above, and 

 holding it horizontally between the thumb and fingers of each hand, turn it con- 

 stantly and with a regular motion in the flame at the point at which it is desired 

 to make the bulb. As the glass at this point softens under the influence of the 

 heat it must be " gathered " by gentle pressure inwards, without however inter- 

 fering with the turning motion. When thoroughly softened, remove from the 

 flame, and holding the pipette at an angle of about 45° from the vertical, blow 

 down the tube with a succession of short " puffs," still maintaining the turning 

 motion with the fingers. As the glass cools the pipette portion below the bulb 

 can be set to any desired angle with the fingers. 



3. To make a constriction in a tube. — Hold the tube in a horizontal position 

 and turn it constantly and with a regular motion in the point of the Bunsen 

 flame at the spot at which it is desired to make the constriction. As soon as 

 the glass has sufficiently softened, remove from the flame and draw the hands 

 steadily apart until the desired constriction is made, maintaining the turning 

 motion with the fingers until the glass has set. The constriction will be abrupt 

 or elongated according to the size of the flame to which the tube is exposed. 



4. To constrict.^ or close, the opening of a tube of small dimensions.- — Holding 

 the tube with its extremity in the edge of the hottest portion of the Bunsen 

 flame, turn it constantly with the fingers until the orifice is seen to contract to 

 the extent required. If it is desired to close the tube entirely, continue the 

 motion until the fusion of the glass is complete and the extremity of the tube 

 has taken a hemispherical form. 



5. To bend a tube of small diameter. — This is preferably done in the flame 

 of an ordinary batswing burner, as the Bunsen flame is apt to produce too sharp 

 and weak a bend, and the soot which gathers on the bent portion of the tube 

 is of advantage in preventing the too rapid cooling and consequent cracking of 

 the tube through unequal contraction. The tube must be rotated slowly and 

 with an even motion between the fingers whilst in the flame, and when it has 

 become sufficiently pliable is removed and bent to the required angle. Should 

 a " U " bend be required, it should be made by bringing the hands together in 

 an upward direction, i.e. with the two ends of the tube in a vertical position 

 and the bend downwards. If too much heat has been applied the sides of thej 

 bend will have a tendency to flatten. Should this tendency be observed it car 

 in a great measure be obviated by closing up one end of the tube with the 

 finger, and while the glass is still soft, blowing somewhat forcibly down the 

 other. Should a bend of more than ordinary neatness be desired it can be 

 obtained by filling the tube with fine dry sand and closing the ends with small 

 corks, or wooden stoppers, before submitting it to the action of the flame. 



6. Capillary tubes and glass inoculating needles. — These are made by heatinj 

 glass tubing or rod in the flame as described above under the head of Pasteur 

 pipettes. When the glass has thoroughly softened, withdraw from the flameJ 

 and holding the tube tightly between the fingers, separate the hands in 

 horizontal line with a steady motion until the desired fineness is obtained. 



7. To cut glass tubing or rod. — In the case of tubes or rods of small diametei 

 it will be sufficient to make a deep scratch or notch at the desired point with 

 small triangular file, or steel knife especially tempered for this purpose. Th< 

 notch should be made by holding the tube in the left hand, the file or knife' 



