Summary
Purified surface factor (SF or activation product) was prepared from canine plasma
and its effect was studied on 22 dogs. It was shown that intravenous injection of
SF increased the coagulability of the circulating blood (in vitro tests) and induced
thrombosis in areas of vascular stasis (in vivo assay). The hypercoagulability was
associated with the injected SF preparation and with no other known clotting factor
increase. A second injection performed 61 minutes after the first was less effective.
The survival period of injected SF seemed to be relatively short. This might be attributable,
in part, to an inhibitory mechanism acting against SF (anti-SF) in plasma. Experimental
evidence of the existence of such an inhibitor and its “progressive” mode of action
is provided. Anti-SF has a variable titer normally, but appears to increase after
the intravenous SF injection in dogs.