BLOOD. 57 



and of the reaction between it and fibrinogen. The aim of the newer theories 

 has been to supply this deficiency. 



Schmidt's Theory of Coagulation. — In a volume 1 containing the re- 

 sults of a lifetime of work devoted to the study of blood-coagulation, 

 Schmidt has modified his well-known theory. His present ideas of the direct 

 and indirect connection of the proteids of the plasma with the formation of 

 fibrin are too complex to be stated clearly in brief compass. He classifies the 

 conditions necessary for coagulation as follows : (1) Certain soluble proteids — 

 namely, the two globulins of the blood — as the material from which fibrin is 

 made. Schmidt does not believe, however, that paraglobulin and fibrinogen 

 react to make fibrin, but believes that fibrinogen is formed from paraglobulin, 

 and that fibrinogen in turn is changed to fibrin. (2) A specific ferment, fibrin 

 ferment, to eifect the changes in the proteids just stated. He proposes for 

 fibrin ferment the distinctive name of thrombin. (3) A certain quantity of 

 neutral salts is necessary for the precipitation of the fibrin in an insoluble form. 



The Relation of Calcium Salts to Coagulation. — It has been shown by a 

 number of observers that calcium salts take an important part in the pro- 

 cess of clotting. This fact was first clearly demonstrated by Arthus and 

 Pages, who found that if oxalate of potash or soda is added to freshly-drawn 

 blood in quantities sufficient to precipitate the calcium salts, clotting will be 

 prevented. If, however, a soluble calcium salt is again added, clotting occurs 

 promptly. This fact has been demonstrated not only for the blood, but also 

 for pure solutions of fibrinogen, and we are justified in saying that without 

 the presence of calcium salts fibrin cannot be formed from fibrinogen. This 

 is one of the most significant facts recently brought out in connection with 

 coagulation. We know that fibrinogen when acted upon by fibrin ferment 

 produces fibrin, but we now know also that calcium salts must be present. 

 What is the relation of these salts to the so-called "ferment"? The most 

 explicit theory proposed in answer to this question we owe to Pekelharing. 



Pekelha ring's Theory of Coagulation. — Pekelharing- succeeded in sepa- 

 rating from blood-plasma a proteid body that has the properties of a nucleo- 

 albumin. He finds that if this substance is brought into solution together 

 with fibrinogen and calcium salts, a typical clot will form, while nueleo- 

 albumin alone, or calcium salts alone, added to fibrinogen solutions, cause 

 no clotting. His theory of coagulation is that what has been called "fibrin 

 ferment" is a compound of nucleo-albumin and calcium, and that when 

 this compound is brought into contact with fibrinogen a reaction occurs, the 

 calcium passing over to the fibrinogen and forming an insoluble calcium 

 compound, fibrin. According to this theory, fibrin is a calcium compound 

 with fibrinogen or with a part of the fibrinogen molecule. This idea is 

 strengthened by the unusually large percentage of calcium found in fibrin 

 ash. The theory supposes also that the fibrin ferment is not present in blood- 

 plasma — that is, in sufficient quantity to set up coagulation — but that it is formed 



1 Zwr Blutlehre, Leipzig 1893. 



2 l T nttrsiirliu)it/rn iibcr (lax Fibriiifcnnrnt, Amsterdam, 1S<)'J. 



