96 BACTERIOLOGY 



attached to a special sterilized blood pipette is thrust into 

 the vein and the desired amount of blood collected (see 

 Fig. 36). It may be allowed to clot if sterile serum is desired, 

 or it may be defibrinated by stirring with the glass rod if a mix- 

 ture of corpuscles and serum is desired, or it 

 may be kept in the fluid state by the addi- 

 tion of sterile 10 per cent solution of sodium 

 citrate so that the final mixture may con- 

 tain 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 withdrawn.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 pre- 

 vents subcutaneous hemorrhage. No dress- 

 ing is required. The inlet to the blood pip- 

 ette 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 the Pasteur 

 bulb pipettes. (See page 33.) 



Blood from small laboratory animals 

 serves as well as human blood for most pur- 

 poses. It may be drawn from the carotid 

 artery by aseptic technic into a special blood 

 pipette the lower end of which is drawn out 



FIG. 37 Pipette into a capillary which is inserted directly 

 with capillary tip for . . , . 



drawing blood fromcaro- into the artery (see Fig. 37). This blood 



WtoNw:) an anima1 ' ma y be defibrinated, citrated or allowed to 



clot. 



Small amounts of sterile blood may be obtained from labora- 

 tory animals without killing them by means of heart puncture. 

 The needle of a Luer glass syringe is inserted through the chest 

 wall, after anesthetizing the animal and shaving and disinfecting 

 the skin, so as to enter the cavity of the right ventricle. A 

 quantity of blood not greater than yV the weight' of the animal 

 may be removed. The needle is withdrawn and the blood quickly 



