1888.] Digestive Changes of Fibrinogen and Fibrin. 367 



February 16, 1888. 



Professor G. G. STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " Note on the Changes effected by Digestion on Fibrinogen 

 and Fibrin." By L. C. Wooldridge, M.D., D.Sc, Assistant 

 Physician to Gny's Hospital. Communicated by Professor 

 Victor Horsley, F.R.S. (From the Laboratory of the 

 Brown Institution.) Received January 27, 1888. 



Fibrinogen is a name conveniently given to a group of proteid sub- 

 stances which can all be converted under certain conditions into 

 fibrin. They exist in blood plasma (in traces in certain kinds of blood 

 serum), and they can be prepared from almost all animal tissues 

 (thymus, testis, brain, liver, kidney, stroma of red corpuscles, &c). 



They differ slightly in their behaviour towards various reagents, 

 but they have a number of characters in common. They are all 

 extremely easily changed by precipitation. In their normal condition 

 tbey are easily soluble in water (" soluble " as casein is dissolved in 

 milk). They are readily precipitated by acetic acid in excess, and 

 dilute mineral acids in slight excess. If more dilute acid be added 

 they are re-dissolved.* 



On adding pepsin to the acid solution and maintaining the mixture 

 at a temperature of 37° for some hours, a very marked precipitate 

 makes its appearance. This precipitate is not dissolved if the artificial 

 digestion be continued for many days. Freshly formed, it is easily 

 soluble in dilute alkalis, but not in dilute acids. It dissolves in 

 strong nitric acid, giving a yellow or yellowish-green solution, which 

 gives a marked xanthoproteic reaction on warming and adding ammo- 

 nia. On incinerating it leaves a markedly acid ash. If it be burnt 

 with a little soda and saltpetre the ash is found to be extremely rich 

 in phosphoric acid. 



The phosphorus is present in the form of lecithin. 



The alcoholic extract of even very small quantities of the precipitate 

 contains relatively very large quantities of lecithin. 



After complete extraction with alcohol there is either no phosphorus 



* It is to be noted that fibrinogens are easily changed in this respect by precipi- 

 tation. 



