54 SCIENCE “PROGRESS 
physiological conditions. In man it has been found that blood 
when shed either does not necessarily coagulate, as in hemo- 
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 BLoop 
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 194° 
showed that in healthy women the average time was 7°75 min.,! 
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 7'8 min.?, My own figures, given 
by another method but taken at the same temperature, average 
8 min. 45 sec. Biirker* 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. 
? Brodie and Russell, Journ. of Phys. p. 403, 1897¢ 
* Pfliiger’s Arch. Ci. 1904. 
