DOUGLAS M. SURGENOR 



with calcium. In addition, the afhnity of not one, but several, 

 of the soluble coagulation components for insoluble salts of the 

 alkaline earth metals, has already been noted (35). These com- 

 ponents include prothrombin, convertin, and proconvertin, and 

 plasma thromboplastin factor B. It is thus not difficult to 

 visualize a complex involving the platelet and the several inter- 

 acting components, with calcium as the cementing substance, 

 aided by other forces which promote the formation of enzyme- 

 subtrate complexes. 



These and other implications are perhaps better understood 

 by referring to the data in Table I, where the familiar list of 

 plasma proteins has been used to estimate the number of mole- 

 cules of the major proteins and the number of blood cells in a 

 unit volume of whole blood, for convenience a volume of 10~^° 1. 

 In these terms there are 120 million molecules of prothrombin 

 for every 25 platelets (5 million molecules per platelet). Assum- 



TABLE I 



Estimated Nlimerical Occurrence of Certain Components in a 

 10~^" Liter Volume of Human Blood" 



Number of cells 

 Component or molecules 



Leukocytes 1 



Platelets 25 



Erythrocytes 500 



Properdin 500,000 



Cholinesterase 670,000 



Caeruloplasmin 66,700,000 



/3-Lipoproteins 89,700,000 



as-Glycoproteins 93,300,000 



Prothrombin 120,000,000 



Fibrinogen 206,000,000 



a-Lipoproteins 350,000,000 



Acid glycoprotein 500 , 000 , 000 



(8i-Metal-combining protein 770 , 000 , 000 



7-Globulins 1,630,000,000 



Albumins 17,300,000,000 



Hemoglobin ( inside erythrocytes ) 1 33 , 000 , 000 , 000 



" Based in part on estimates from data in references 17, 20, 27, and 29. 



670 



