THE BLOOD. 545 



Naturally it does not necessarily follow that all cases of hemophilia result 

 from the same cause. Perhaps in different cases, different links in the 

 whole chain of processes may be missing. We have introduced this dis- 

 cussion here not alone because it apparently sheds light upon the process 

 of coagulation, a fact to which H. Sahli first called our attention, but 

 because it seems to us as highly significant that such an extremely localized 

 anomaly in the whole course of a fermentative action should prove to be 

 hereditary. . 



We have up to this point failed to answer the question why the blood 

 does not coagulate in the blood-vessels of the body under normal con- 

 ditions. It is a priori not so easy to see why conditions could not pre- 

 vail within the blood-vessels which would bring the fibrin-ferment into 

 activity. On the other hand, the fact that the coagulation process depends 

 upon the harmonious action of several distinct factors, presents several 

 possibilities whereby the coagulation in the blood-vessels themselves 

 may be prevented. It is merely necessary to prevent the bringing into 

 activity of the fibrin-ferment. The following experiment 1 brings to our 

 attention still another factor which we have not considered in the coagu- 

 lation of blood. If blood is collected under vaseline or oil, it remains 

 perfectly fluid for hours. It can be stirred with a greased rod without its 

 coagulating. If, on the other hand, the precaution is- not taken to grease 

 the rod, coagulation at once takes place upon stirring. It is even possible 

 to centrifugalize blood that has been collected in paraffined vessels, and 

 thus obtain plasma, which similarly will not clot for a considerable length 

 of time if it is kept in greased or paraffined vessels. On the other hand, 

 if such blood is poured into an ordinary glass vessel, it will clot immediately. 

 The contact of the blood with something that it can wet, seems to start the 

 coagulation. As this paraffined plasma, after the calcium salts have been 

 removed from it, does not coagulate when brought into contact with 

 foreign bodies, it is out of the question to believe that it contains an active 

 ferment. By the process of exclusion, we may conclude that the contact 

 with a foreign body in some way accelerates the transformation of the 

 zymogen into active ferment. One might assume from this that the reason 

 the blood does not coagulate in the blood-vessels, with intact intima, is 

 that the conditions are similar to that of the greased vessels outside of the 

 body. In fact, we know that if the intima is in any way injured, intra- 

 vascular coagulation readily sets in, which is called a thrombus when it 

 merely stops up the blood-vessel which is injured, but is known as embo- 

 lism when the coagulation influences other blood-vessels as well. The 

 blood is continually wetting the intima of the blood-vessel walls. The 



1 Briicke: Virchow's Arch. 12, 100 (1857). Freund: Wiener Med. Jahrbiicher, 1888, 

 259, and 1889, 554. Bordet and Gengou: Ann. Institute Pasteur, 17, 822 (1903); 18, 

 1 (1904). 



