An estimation of the coagulation-time of the blood is of little value unless one is acquainted with the many factors that affect it. Some of these factors are extrinsic, acting on the shed blood ; others are intrinsic, acting on the blood while it is still in the vessels. Of the former factors many are introduced by the method employed for measuring the clottingtime. The clotting-time obtained by any one of the different methods employed is influenced by the factors of error inherent to that method. It is important, therefore, to be familiar with the sources of error inherent in the method used.
1. METHODS EMPLOYED FOR MEASURING THE CLOTTING-TIME OF THE BLOOD
The methods employed for measuring the coagulation-time of the blood may be grouped according to the similarity of the factors involved. In one group the blood is received in capillary tubes, in another on wire loops; the