The Coagulation Time of the Blood in Man 327 



') cm. mark. A carefully prepared white horse-hair is then introduced into 

 llie tube, so that a segment of it is surrounded by blood. At intervals of time 

 the hair is pulled a short distance out of the tube. As coagulation advances 

 small masses of fibrin and red blood corpuscles will be found sticking to the 

 hair, but later still the blood becomes so solid that none adheres to it. 

 This is taken as the end-point, 



V^ierordt (27) fully recognised the importance of a uniform method of 

 obtaining the blood, and the necessity of always having the same amount 

 of contact with foreign bodies. He also mentions that the temperature 

 should, as far as possible, be constant. - 



He made a large number of estimations, principally on himself, and he 

 gave the first list of coagulation times in disease. 



His results were very variable. The limits in the case of his own blood 

 were from 3^ to 17^ minutes, and he was unable to establish any regularity 

 in the fluctuations. These must have been due mainly to changes of 

 temperature and to want of reliability in the end-point. 



Buckmaster's Method. 



The method is based on the fact that, when a loop of wire is drawn 

 through a drop of blood so that a film of blood is taken up by it, the 

 corpuscle.^ can be observed by the aid of a lens to flow in response to 

 changes in the position of the loop. Thus when it is held vertically they 

 can be seen to fall slowly downwards until a clear circle of plasma is left 

 at the upper pole, while in the horizontal position tliey spread themselves 

 evenly over the film. As time goes on the flow of the corpuscles becomes 

 slower and more impeded until a moment arrives at which no movement 

 can be seen. The blood is then considered to have coagulated. 



The apparatus is devised with the object of keeping the film of blood at 

 a constant temperature. It consists of a box, the lower part of which is 

 filled with water. The film is in an inner chamber. Panes of glass are 

 fitted in the sides so that it is possible to sec the blood when it is in position. 



When the wire with its film of blood has been introduced all openings 

 are closed, and the film can be rotated from outside the box. The water is 

 warmed from below, and a thermometer whose bulb is in the inner chamber 

 records the temperature of the air surrounding the blood. 



This is an extremely original and ingenious method. No work has as 

 yet, so far as I know, been done with it. Buck master (28) himself gives 

 only a few times taken at slightly different temperatures. 



In attempting to make a series of observations by it at the same tem- 

 perature, I found that temperature variations were apt to occur even during 

 the course of an experiment, while it was altogether impracticable, without 

 tedious waiting and manipulation, to get a series of times taken at a 

 constant temperature. This is not remarkable when it is remembered that 

 whenever the wire loop is removed for cleaning and filling with a fresh 



