318 Addis 



temperature is not kept constant cannot yield comparative results which 

 may be relied upon. 



3. The Contact of the Blood with the same Amount and Kind 

 of Foreign Body in each Observation. 



A foreign body, as regards blood-coagulation, may be detined as any- 

 thing which hastens or retards the coagulation time. 



Besides the intact endothelial lining of the vessels, there is only one 

 class of substances which may be said not to act as foreign bodies, i.e. the 

 oils. I do not think that the ordinary commercial mineral oils can, strictly 

 speaking, be entirely excluded from classification as foreign bodies, for I 

 found that the coagulation time of blood surrounded from the monient it 

 issued from the wound by '" motor spirit " was less than the time taken 

 when ordinary paraffin oil was used. Paraffin oil gave a time of from 70 

 to 80 minutes, while with Pratt's Motor Spirit it was 50 to GO minutes. 

 Nevertheless, their action as foreign bodies is so slight, in comparison 

 with that of other substances, that they may be considered as having 

 practically no effect at all. 



This fact may be utilised to estimate the effect of foreign bodies on the 

 coagulation time. For, by placing a drop of blood in partial contact with a 

 foreign body of constant nature and surrounding it elsewhere by oil, the 

 complicating effect of otTier substances is excluded, and the resulting 

 coagulation time gives an indication of the influence of that particular 

 foreign body. 



In the following experiments coagulation was said to have occurred 

 when a visible mass of fibrin was left after drawing off the fluid portion of 

 the drop with filter paper. I found that, when blood was drawn under 

 paraffin oil in a vessel lined with paraffin-wax, it took 70 to 80 minutes 

 to coagulate. This, then, maj^ be taken as representing the coagulation 

 time when the process is allowed to occur without the intervention of any 

 foreign body. In this case coagulation is due simply to that amount of 

 injury which, the blood receives in its passage from the wound, and to the 

 thrombokinase added to it from the tissues of the wound. 



Drops of blood which were placed on clean glass slides and then 

 innnersed, blood downwards, in oil, took from 20 to 26 minutes to coagulate. 

 Here the only foreign body was glass. 



Other slides were coated with a smooth film of paraffin-wax and drops 

 of blood placed on them. In this case the foreign body was air, and the 

 coagulation time was 10 to 16 minutes. 



When the blood was exposed to both glass and air it coagulated in 

 o minutes. These results are of course rough, for no attempt was made to 

 keep the temperature constant ; but tliey were all done within 3 hours on the 

 san»e afternoon, and they serve to indicate that different foreign bodies have 

 different effects on the coagulation time. They also make it clear tiiat the 



