K. LAKI 
477 
80 1- 
60 
40 
20 
COW THROMBIN 
J I I 1 I I I I I L 
FIBRINOGEN 
Figure 1. 
80 I- 
60 
20 — 
HORSE THROMBIN 
J I L 
J_ 
-vv^^ .S^^ 
FIBRINOGEN 
Figure 2. 
J_ 
J_ 
The points in figures 1 and 2 represent the number of thrombin units found when cow and horse thrombin 
clotted the various fibrinogens (shown on the abscissa). Cow and human thrombins exhibited the greatest 
variations in clotting the various fibrinogens. In case of horse thrombin, the variation in the rate of clot- 
ting was very small. 
to give clotting times, usually between 10 to 90 
seconds. Solutions of the various fibrinogens to 
be clotted contained identical amounts of fibrino- 
gen under identical conditions. The speed of the 
clotting reaction was measured from the addi- 
tion of thrombin in the Klett colorimeter by fol- 
lowing the development of turbidity. For the 
clotting time, we selected arbitrarily the time 
needed for the turbidity to reach about one- 
third of its final value. The clotting times were 
converted into thrombin units. A thrombin unit 
is the logarithm of the reciprocal of the clotting 
time. Since clotting follows the kinetics of a 
first order reaction, thrombin units are expres- 
sions of the velocity constants. 
By means of the thrombin units, the various 
fibrinogens could be ordered according to the 
ease with which they interacted with a given 
thrombin (see Figures 1 and 2, and Table II). 
It is seen from Table II that chicken thrombin 
clotted the fibrinogens of rabbit, sheep, goat, 
pig, ox, horse, dog, monkey, and man faster 
than its own. Horse thrombin, on the other 
hand, clotted all of them with roughly the same 
speed (Figure 2). The variation of speed is not 
very great. Human thrombin was found to ox- 
Table II. — Thrombin 
The columns in this table show the fibrinogens in decreasing order corresponding to the speed with which these were 
clotted by a thrombin (given at the head of the column). The fibrinogens reacting fastest with the thrombin 
>are at the top of the columns. Places where goat and sheep fibrinogen appear together are marked by circles. 
The entries marked with squares show those four instances where the clotting parameters of sheep and goat 
fibrinogen is separated by others. 
Monkey 
Dog 
Pig 
Rabbit 
Sheep 
Goat 
Cow 
Man 
Turkey 
Chicken 
Fibrinogen Rabbit 
Sheep 0 
Sheep □ 
Dog 
Goat □ 
Dog 
Rabbit 
Cow 
Rabbit 
Goat 0 
Dog 
Goat O 
Rabbit 
Man 
Rabbit 
Man 
Sheep 0 
Rabbit 
Goat 0 
Sheep 0 
Cow 
Cow 
Goat □ 
Cow 
Man 
Rabbit 
Goat O 
Sheep □ 
Sheep O 
Rabbit 
Sheep O 
Rabbit 
Pig 
Rabbit 
Sheep □ 
Monkey 
Dog 
Dog 
Chicken 
Pig 
Goat O 
Man 
Cow 
Sheep 0 
Dog 
Cow 
Cow 
Goiit □ 
Cow 
Man 
Man 
Dog 
Dog 
Goat 0 
Cow 
Horse 
Horse 
Mar: 
Pig 
Cow 
Horse 
Pig 
Horse 
Horse 
Horse 
Sheep □ 
Pig 
Hcrfi? 
Horse 
Dog 
Monkey 
Monkey 
Man 
Pig 
Pig 
Pig 
Man 
Pig 
Dog 
Horse 
Pig 
Horse 
Monkey 
Monkey 
Monkey 
Goat □ 
Monkey 
Monkey 
Man 
Monkey 
Chicken 
Chicken 
Chicken 
Chicken 
Chicken 
Chicken 
Chicken 
Chic.tc 
Monkey 
Chicken 
