BLOOD. 59 



Schmidt prepared solutions of fibrin ferment originally by adding a large 

 excess of alcohol to blood-serum and allowing the proteids thus precipitated 

 to stand under strong alcohol for a long time until they were thoroughly coagu- 

 lated and rendered nearly insoluble in water. At the end of the proper period 

 the coagulated proteids were extracted with water, and there was obtained a 

 solution which contained only small quantities of protcid. It was found that 

 solutions prepared in this way had a marked effect in inducing coagulation 

 when added to liquids, such as hydrocele liquid, that contained fibrinogen, 

 but did not clot spontaneously or else clotted very slowly. It was after- 

 ward shown that similar solutions of fibrin ferment are capable of setting up 

 coagulation very readily in so-called salted plasma — that is, in blood-plasma 

 prevented from clotting by the addition of a certain quantity of neutral salts. 

 It was not possible to say whether the coagulating power of these solutions 

 was due to the small traces of proteid contained in them, or whether the pro- 

 teid was merely an impurity. The general belief for a time, however, was 

 that the proteids present were not the active agent, and that there was in solu- 

 tion something of an unknown chemical nature which acted upon the fibrinogen 

 after the manner of unorganized ferments. This belief was founded mainly 

 upon three facts : first, that the substance seemed to be able to act powerfully 

 upon fibrinogen, although present in such minute quantities that it could not be 

 isolated satisfactorily ; second, it was destroyed by heating its solutions for a few 

 minutes at 60° C. ; and, third, it did not seem to be destroyed in the reaction 

 of coagulation which it set up, since it was always present in the serum squeezed 

 out of the clot. Schmidt proved that fibrin ferment could not be obtained 

 from blood by the method described above if the blood was made to flow im- 

 mediately from the cut artery into the alcohol. On the other hand, if the shed 

 blood was allowed to stand, the quantity of fibrin ferment increased up to 

 the time of coagulation, and was present in quantity in the serum. Schmidt 

 believed that the ferment was formed in shed blood from the disintegration 

 of the leucocytes, and this belief was corroborated by subsequent histological 

 work. It was shown in microscopic preparations of coagulated blond that the 

 fibrin threads often radiated from broken-down leucocytes — an appearance 

 that seemed to indicate that the leucocytes served as points of origin for the 

 deposition of the fibrin. When the blood-plates were discovered a great deal 

 of microscopic work was done tending to show that these bodies also are con- 

 nected with coagulation in the same way as the leucocytes, and serve probably 

 as sources of fibrin ferment. In microscopic preparations the fibrin threads 

 were found to radiate from masses of partially disintegrated plates ; and, more- 

 over, it was discovered that conditions which retard or prevent coagulation of 

 blood often serve to preserve the delicate plate- from disintegration. At the 

 present time it is generally believed that there is derived from the disintegra- 

 tion of the leucocytes and blood-plates something that is necessary to the 

 coagulation of blood, but there is sonic difference of opinion as to the nature 

 of this substance and whether it is identical with Schmidt's fibrin ferment. 

 Pekelharing thinks that the substance sel free from the corpuscles and plates 



