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physiological conditions. In man it has been found that blood 

 when shed either does not necessarily coagulate, as in haemo- 

 philia, or does so slowly or rapidly. We must admit that the 

 appearance of fibrin in shed blood is definite evidence of its 

 altered state. This may take place within 10 to 20 seconds from 

 the time blood is shed from a wound, for when examined as a 

 stretched film at the temperature of the body in a moist chamber, 

 a thread of fibrin some millimetres in length can be lifted from 

 the film. In this interval of time, therefore, a gross change 

 occurs — the appearance of fibrin, which does not exist in blood ; 

 and it is permissible to suggest that possibly blood commences 

 to undergo other changes less easy to recognise immediately 

 it leaves the body. 



2. The Coagulation Rate of Human Blood 



A knowledge of the rate of coagulation of human blood is 

 considered by many clinical observers to be of diagnostic 

 importance. It is difficult, if not impossible, to accurately 

 ascertain this rate, since the results of different observers are 

 conflicting, and this is due partly to the diversity in the methods 

 employed as well as to the inherent difficulties in carrying out a 

 series of successive experiments under exactly, similar con- 

 ditions. In this country most of the data have been obtained by 

 the methods suggested by Sir Almroth Wright. The figures of 

 this observer for normal human blood at a temperature of 20 C. 

 are about 4 min. 50 sec. A series of between 300 and 400 

 observations made by this method at a temperature of 19/4 

 showed that in healthy women the average time was 775 min., 1 

 though it may be as short as 5 or as long as 10 minutes. 

 The average value obtained for normal men by an entirely 

 different method at 20 is given at y'S min. 2 My own figures, given 

 by another method but taken at the same temperature, average 

 8 min. 45 sec. Burker 3 has devised yet a fourth method, and 

 his recent figures show that the rate varies between 6 and 

 7*5 min. at 20 , although in the same individual, according to the 

 time of day, amount of exercise, or kind of food, the rate of 



1 Douglas, Brit. Med. Journ. March 26, 1904. 



2 Brodie and Russell, Journ. of Phys, p. 403, 1897. 



3 P finger's Arch. cii. 1904. 



