90 LABORATORY COURSE IN SERUM STUDY 



(A) When possible from a vein, 3 to 5 c.c. in a test tube for serum, 

 10 drops in 5 c.c. of a solution containing 1 per cent sodium 

 citrate and 0.9 per cent sodium chloride, for the red cell emulsion. 



(B) By pricking the finger with a Hagedorn needle and milking 

 out from 1 to 2 c.c. of blood which is collected in a Wright capsule 

 for serum and 10 drops in citrate-salt solution for cells. 



Students make Wright capsules and collect specimens of blood 

 from each other. The capsules are of heavy glass tubing, 7 to 8 mm. 

 in diameter, about 10 cm. long, and drawn to a capillary opening of 

 about 1 mm. diameter at each end. They are laid on the table and drops 

 of blood expressed from the finger are allowed to enter them by capillary 

 action. When the capsule is two thirds full, the blood is allowed to clot 

 and the open end of the capsule is sealed in the flame, great care being 

 taken not to heat the blood. Serum is obtained by centrifugalizing the 

 capsules and cutting them with a small file. 



The cell emulsions are prepared by washing the citrated blood twice 

 with salt solution and making up to 5 per cent by comparing the opacity 

 with that of a 5 per cent sheep cell suspension, or by measuring with 

 capillary pipette 1 volume of sedimented human cells and 19 volumes 

 of saline. 1 



Each student should make 12 Wright capillary pipettes of strong 

 glass tubing, 4 to 5 mm. in diameter. These pipettes are made by cut- 

 ting the tubing into pieces about 10 cm. inches long, heating the center of 

 each piece to melting and drawing out to a capillary of about 1 mm. 

 diameter and 10-12 cm. inches long. The capillary is then broken at the 

 middle, giving two pipettes. Adjust nipple to the pipettes. Make a 

 mark on the capillary end of each pipette near the hilt. Draw up 1 

 volume of serum to the mark, then a small buble of air, then another 

 volume of serum, and another bubble of air, and then a volume of the 

 cells which are to be mixed with the serum ; (the serum is used in excess 

 because in this way it is sometimes possible to detect a weak hsemolytic 

 action which would otherwise be overlooked on account of the low com- 

 plement activity of human blood). Draw the mixture into the body of 

 the pipette and seal the capillary tip in the flame. Mix the fluid by 

 rotating the pipette. Remove the nipple. Throughout these steps 

 keep the pipette approximately horizontal so that the fluid remains in 

 the body of it and does not flow to either end. Seal the open end of the 

 pipette by dipping in melted paraffine. Mark the pipette with a glass 

 pencil, using the number assigned to the serum as the numerator, that 

 assigned to the ce.lls as the denominator, of a fraction. 



1 It is not necessary in practical work to wash the cells. Three or four drops of 

 blood in citrate salt solution furnishes satisfactory material. 



