540 LECTURE XXIII. 



that this activator is likewise present in the blood in an inactive condition, 

 and is only changed into the active condition by the presence of calcium 

 salts. 1 



We must recall one other fact that we met with in discussing the diges- 

 tive ferments. We mentioned that the bile, and the intestinal juices in 

 general, had the property of augmenting the action of the pancreatic juice. 

 According to our present knowledge, this does not consist merely in chang- 

 ing zymogen into ferment. The above-mentioned secretions accelerate 

 directly the fermentation process. Until we understand the nature of 

 ferments better, there is naturally but little prospect of our being able 

 to comprehend the accelerating effect. We can only mention the fact, 

 and state in addition that there are other substances known which 

 tend to retard the action of ferments without in any way injuring them 

 directly. 



We must also ascertain whether there are substances which tend to 

 accelerate the action of the fibrin-ferment. It has indeed been long recog- 

 nized that there are substances which accelerate the clotting of the blood. 

 Even Buchanan noticed an acceleration produced by certain tissues. 

 Rauschenbach 2 has proved beyond question that there are substances 

 present in the cells of the tissues which aid in the formation of the clot. He 

 found a particularly favorable action on the part of those tissues which 

 were rich in nuclein substances. Foa and Pellacani 3 showed further that 

 the injection of the juices from various tissues caused intravascular coagu- 

 lation. This caused a tedious, unfruitful discussion as to whether the 

 substances present in the cells of the tissues were to be considered as 

 corresponding to the fibrin-ferment, or whether they merely augmented 

 its action upon the plasma. The first assumption is a tempting one. In 

 the first place, according to many observations the leucocytes are the ante- 

 cedents of the fibrin-ferment. It would be of itself not inconceivable that 

 other cells in the body should produce similar, or the same, products, 

 especially as it is well known that after death a coagulation takes place in 

 the cells which may be considered as perfectly analogous to the clotting of 

 blood. 



Certain observations, however, make it seem more probable that the 

 coagulation action of the tissue extracts depends upon a quite different 

 process than the direct introduction of fibrin-ferment. Above all, the work 



1 It is probably true that the lime salts do not directly cause the activation of the 

 fibrin-ferment zymogen, for it is not easy to see otherwise how the blood can contain 

 the two substances side by side without their reacting together. The calcium salts are 

 only brought into activity when the fibrin-ferment zymogen has been changed in some 

 way. 



3 Ueber die Wechselwirkungen zwischen Protoplasma und Blutplasma. Dorpat, 

 1883. 



Arch. Science med. 7, 113 (1883). 



