68 
Journal of Agricultural Research 
Vol. XI, No. 3 
2. Cow serum. —This is obtained by bleeding a normal cow from 
the jugular vein into a sterile flask containing glass beads. The blood 
is defibrinated and then centrifuged and the clear serum drawn off. This 
should also be absolutely clear and free from red cells. The cow serum is 
then heated at 54 0 C. for half an hour, after which it is carbolized 0.5 
per cent and stored in dark-colored bottles in the ice chest. The cow 
serum can be used for four to six weeks. 
3. Sheep red blood corpuscles. —A sheep is bled from the jugular 
vein into a sterile flask containing glass beads. The blood is defibri¬ 
nated and then centrifuged, the serum drawn off, and the corpuscles 
washed four times with a salt solution (0.83 per cent). 
titration of the cow serum 
Constant amounts of horse serum (0.1 c. c.) and sheep blood (0.1 c. c. 
of a 5 per cent suspension) are used. It is now necessary to determine 
the smallest amount of cow serum that will cause conglutination of 
0.1 c. c. of a 5 per cent suspension of sheep-blood corpuscles with 0.1 
c. c. of fresh normal horse serum. Tubes of 13 mm. diameter and 9.5 
cm. length are used in the test. 
The results of the titration are given in Table I. 
Table I .—Titration of cow serum 
Tube No. 
Comple¬ 
ment.® 
Salt so¬ 
lution. & 
Inactivated cow serum, c 
Sheep- 
blood 
corpus- 
cles. d 
Re¬ 
sult. e 
C. c. 
0. I 
C.c. 
0. 7 
C. c. 
0. I 
C. c. 
O. I 
+ 
+ 
+ 
+ 
± 
. I 
. 2 
• 05 =0. 5 
, 02 =0. 2] 
. 1 
. I 
O 
. 6 
1 
. I 
A . 
. I 
. 7 
. OI =0. Ij 
fi:io 
. I 
c.*. 
. I 
• 3 1 
. 005=0. 5 
. 002=0. 2 
. 1 
6 . 
. I 
O 1 
. 6 
tinoo 
. I 
± 
7. 
. I 
. 7 
. 001=0. Ij 
. I 
7 8. 
. I 
. 8 
. I 
. 08 
. I 
. 1 
% } . 
7 10.. 
.09 
. 1 
a Fresh normal horse serum. 
6 0,85 per cent. 
c Cow serum inactivated at 54® C. for half an hour and carbolized 0.5 per cent. 
d Five per cent suspension of washed sheep-blood corpuscles. 
e +*= conglutination; ± = partial conglutination; —=no conglutination. 
/ Control. 
In Table I the smallest quantity of cow serum producing complete 
conglutination of o.i c. c. of a 5 per cent suspension of sheep-blood cells 
in 2 hours is represented by tube 4 as 0.01 c. c. Twice this amount is 
used in the test, making the titer of the cow serum 0.02 c. c. The cow 
serum need only be titrated once, provided the complement is derived 
from the same horse each time and the same sheep is always used to 
obtain the red-blood cells. The conglutination system is now titrated 
(Table II). 
