BLOOD-SERUM. 59 
VIII. Blood-serum (Zéffer’s). 
(a) Receive freshly drawn beef blood in sterile 
jars. 
(2) Allow twenty minutes for coagulation to 
begin, then with a sterile glass-rod break up any 
adhesions between the coagulum and the jar. 
(c) Allow the jars to stand twenty-four hours in 
the ice-box. 
(2) Siphon off the clear serum.' 
(e) To 3 parts of serum add 1 part of 1 per cent. 
dextrose bouillon.” 
(/) Adjust to + 0.8 per cent. 
(g) Distribute in tubes and solidify with a slant- 
ing surface by heating for three hours in a blood- 
serum coagulator. 
(2) Sterilize in the steam sterilizer for twenty 
minutes on three successive days. 
1If the serum is not clear, filter through the coagulum 
left after the filtration of bouillon, as suggested by Hill. 
2 If 1.25 per cent. glycerin is added also, it seems to pre- 
vent the tubes from drying. 
