CH. X.] 



BANG'S METHOD. 



255 



A paper is held in a small spring clip and the clip and paper 

 are weighed together as described on p. 388. 



The hand of the subject is washed in warm water and dried. 

 The subject is instructed to swing the arm backwards and forwards, 

 keeping the hand as low as possible. The finger is pricked with a 

 sterile bayonet-pointed probe on the back of the finger about 

 J inch above the nail. A piece of rubber tubing is wound tightly 

 round the middle joint of the finger. On firmly flexing the finger 



Fig. 32. Apparatus for titration in an atmosphere of CO 2 . 



A. Wash bottle containing water. 



B. Tube fitted into flask so that the iodine can fall from burette directly 

 into the fluid. 



the blood usually wells up in sufficient amount. The blood is taken 

 up on the paper, until the paper is fairly covered. It is undesirable 

 to have the paper fully saturated with blood. The paper and clip 

 are immediately weighed on the torsion balance, and the weight of 

 blood taken is thus known. A convenient amount is about 120 mg. 



B. By means of a pipette (see 6 above). 



The pipette being cleaned and dried, and the absorbing paper 

 ready, the finger is pricked as described above. When a large drop 



