BLOOD. 355 



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 fibrinogeu in turn is changed to fibrin. (2) A specific ferment, fibrin 

 ferment, to effect 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 most 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"? This question 

 has been differently answered in two recent theories of coagulation. 



Pekelharing's Theory of Coagulation. Pekelharing 1 succeeded in sepa- 

 rating from blood-plasma a proteid body which 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 nucleo- 

 albumin alone, or calcium salts alone, added to fibriuogen 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 

 after the blood is shed. The nucleo-albumin part is derived from the cor- 

 puscles of the blood (leucocytes, blood -plates), which break down and go into 

 solution. This nucleo-albumin then unites with the calcium salts present in 

 the blood to form fibrin ferment, an organic compound of calcium capable of 

 reacting with fibrinogen. The theory is a simple one ; it accounts for the 

 1 Untersuchungen iiber das Fibrinferment, Amsterdam, 1892. 



