98 



BACTERIOLOGY 



with alcohol and bichloride and dried. An elastic bandage is 

 applied about the arm to distend, the veins. A sterile needle 

 attached to a special sterilized blood pipette is thrust into the 



vein and the desired amount of 

 blood collected (see Fig. 37). It 

 may be allowed to clot if sterile 

 serum is desired, or it may be 

 defibrinated by stirring with the 

 glass rod if a mixture of corpuscles 

 and serum is desired, or it may be 

 kept in the fluid state by the ad- 

 dition of sterile 10 per cent solution 

 of sodium citrate so that the final 

 mixture may contain i per cent of 

 citrate. The bandage is removed 

 from the arm before the needle is 

 withdrawn. Pressure over the 

 wound with cotton wet in alcohol 

 for five minutes prevents sub- 

 cutaneous hemorrhage. No dress- 

 ing is required. The inlet to the 

 blood pipette is closed by kinking 

 the rubber tube. The blood or the 

 serum is subsequently handled by 

 means of sterilized pipettes, and 

 most conveniently by means of 

 Pig. 37.— Pipette with needle at- the Pastcur bulb pipettcs. (See 



tached for drawing human blood Tjoge 22 ^ 

 from a vein for use in culture media. H 8 oov 

 The glass rod inside is used to defi- Blood from Small laboratory 



rina e e 00 . animals serves as well as human 



blood for most purposes. It may be drawn from the carotid artery 

 by aseptic technic into a special blood pipette, the lower end of 

 which is drawn out into a capillary ,which is inserted directly into 

 the artery (see Fig. 38). This blood may be defibrinated, ci- 

 trated or allowed to clot. 



