The Coagulation Time of the Blood in Man 325 



with Bogg's (2) modification of it. I found that with its use the coagula- 

 tion time varied considerably in consecutive observations on the same 

 person. Thus a time of 4 minutes might be followed by one of 12 minutes, 

 and so on, without any regularity. Moreover, simultaneous observations 

 with two similar coagulometers gave contradictory results. These dis- 

 crepancies appear to have been due either to temperature variations or to 

 the want of definiteness of the end-point, or to actual fallacies in connection 

 with the end-point. 



The arrangement for the circulation round the air chamber of water 

 ;it a constant temperature is inadequate to keep the temperature of the air 

 which surrounds the blood constant. Not only is the cone tkken off at the 

 end of each observation, leaving the chamber in direct communication with 

 the air of the room, but fresh air of unknown temperature is blown in 

 every half minute or so when the cone is in position. The uselessness of 

 the water-jacket is so apparent that, so far as I am aware, no one has used 

 it except Brodie and Russell (1), who recorded the effect of running water 

 at different temperatures through it. 



Another cause of error is the indefiniteness of the end-point. 

 Hinman and SI ad en (36) point out that different observers have used 

 three different stages as end-points. Thej" believe that a radial elastic 

 movement is the most definite occurrence to fix on as indicating coagulation. 

 I find, however, that it is very difficult to be sure of the exact time of occur- 

 rence of this condition. Often it is found to be present quite early, but a 

 blast of air stronger than usual causes it to disappear entirely. In these 

 3ases it was due simply to agglutination of the corpuscles In cases where 

 agglutination ia allowed to become advanced, as when the blood is not set 

 in motion immediately after it is introduced into the apparatus, no amount of 

 blowing is suflRcient to break it up. The blood appears to be coagulated, yet 

 on removing the cone and examining it directly no coagulum can be found. 



1 believe that this end-point is due partly to tigglutination and partly 

 to coagulation. If the blowing is done frequently and strongly, the amount 

 of agglutination is slight or absent and the coagulation time is relatively 

 long. If, on the other hand, the blowing is done at longer intervals and 

 lightly, the end point is really due to agglutination, and the resulting time 

 is short. 



Hayem's Method, 



Blood is received in a test-tube which is then tilted at intervals until the 

 blood becomes so solid that the level no longer changes with each move- 

 ment of the tube. Dastre and Floresco (39) and Brat (40) have worked 

 with this method. Floresco thinks that it gives more accurate results 

 than either Wright's or Vierordt's methods. Bezan(;on and Labbe 

 (41 ) have used a slightly modified form of it. A great disadvantage is the 

 considerable quantity of blood which is required. Moreover, Hay em 

 appears to have made no attempt to exclude temperature variations. 



