BACTERIOLOGICAL PIPETTES 15 



lary pipette is made by taking a piece of i/4-in. soft German glass tub- 

 ing, about 6 inches long, and heating in the middle in a Bunsen flame, 

 revolving the tubing while heating it. When it becomes soft in the 

 center, remove from the flame and with a steady even pull separate the 

 two ends. The capillary portion should be from 18 to 20 inches in 

 length. When cool, file and break off this capillary portion in the 

 middle. We then have two capillary pipettes. By using a rubber 

 bulb, such as comes on medicine droppers, we have a means of sucking 

 up and forcing out fluids by pressure with the thumb and forefinger of 

 the right hand. The bulb should be pushed on about 1/2 to 3/4 in.; 

 this gives a firmer surface to control the pressure on the bulb. 



A bacteriological pipette is made by drawing out a g-inch piece of tubing about 

 3 inches at either end, then heating in the middle we draw out and have two pipettes 

 similar to the one shown in the drawing. A piece of cotton is loosely pushed in 

 just above the narrow portion. These may be wrapped in paper and sterilized for 

 future use. They may be made perfectly sterile at the time of drawing out. 



Where gas is not at hand, the Barthel alcohol lamp gives a flame similar to that 

 of the Bunsen lamp and is equally satisfactory for heating glass tubing. By making 

 a collar with a lateral opening to fit the burner of a Primus lamp a powerful side- 

 flame is obtained which is almost as suitable for glass blowing as the Bunsen blast 

 usually employed. 



