BLOOD-SERUM. 127 



sealed in a gas-flame, the loose ligature tightened, 

 the wound closed, and the bulb containing the blood is 

 set aside in a cool place until coagulation has occurred. 

 The serum is most easily withdrawn from the bulb by 

 means of a pipette, closed above with a cotton-plug, and 

 supplied with a piece of rubber-tubing about one-half 

 metre long, with glass mouth-piece. By holding the 

 pipette in the hand and sucking upon the rubber tube 

 one can more easily direct the point of the pipette than 



FIG. 20. 



a 



Nuttall's bulb for collecting blood-serum under antiseptic precautions. 



if it is used in the ordinary way. The bulbs are 

 easily blown, and after having been sealed at the point 

 ' and plugged with cotton can be kept on hand just as 

 are sterilized test-tubes. An ordinary test-tube drawn 

 out at the bottom to a fine point may be substituted 

 for the pear-shaped bulb with equally satisfactory 

 results. 



Latapie ' describes an apparatus for the collection of 



1 Latapie : Aunales de 1'Institut Pasteur, 1900, vol. xiv. p. 106. 



