111.. 



Thrombin d«"'s no1 •• v i^i in blood plasmi 

 glass tube is inserted into an artery ant blood 



<•oli.il, the precipitate after standi) eld no throi ibin 



when triturated with water. Quite clearly, then 



produced ;it the time the bl I clots, and 1 1 1 « - qui 



it produced froml It will !>•• remembered that, wh< 

 amined under the microscope during the <•!< »t 1 1 

 threads are Been to Btarl from t'"<-i which corresp* 

 Lets. It would appear therefore thai the tin-.. ml. in tn 

 Borne Bubstance thai is shed forth from the platelets duri 



tegration which they undergo shortly after the bl i 



Btance is called prothrombin. The platelets or their 



megacaryocytes of red bone marrow, are probably i I I 



for clotting may occur in the complete al n it 



appears to come from the leu< ytes. Prothrombin apj illy 



in the fluid used to perfuse red bone marrow outside the bod) I>:i' 

 and Drinker ). 



To Bum up whal we have bo far 1 « • .• » t ■ I. it may I 



process «>i' clotting starts with the disintegration of blood 

 probably of leucocytes, as a resull of which there is shi 

 plasma a Bubstance "•ailed prothrombin, which immediately 



omes activated or converted into thrombin. The ,; mbin ti 

 tacka a protein present in plasma called fibr t in 



thread-like form the insoluble protein, fibrin. Hut this doei 

 plete the history, for al leasl two other important 



play; tin • is the presence "f soluble calcium salts, and tl 



of peculiar Bubstances «i*-iix •-«! from the tissues out 



and called thromboplastic Bubstanci thromboplastin H SV< 



must now consider the action of these two 



The Influence of Calcium Salts. \ x plained, tl. 



Boluble calcium Balta are necessarj for clotl 

 Bervation that tin- process is entirely p 

 blood is mixed with Boluble oxalati 

 mighl I"- made on the Bcore that tin 

 That Buch is nol the ease is indicated by tl 



• 



blood or plasma is dialyzed agaiiiHl phys 

 the soluble oxalate has been removi 

 immediately Buperveni 

 question arises as t,. how tl • nun i. 



1 thai it is concerned in • 



2 that it is i.. [1 



.•an quite readil) be si ..w p thai 



