1885.] Fibrin-yielding Constituents of Blood Plasma. 263 



Now this serum contains fibrin ferment ; but inasmuch as ferment 

 does not cause anything more than a trace of clot in peptone plasma, 

 the serum must evidently contain some special body which renders the 

 plasma coagulable by ferment. It must contain the precursor of the 

 fibrinogen which, as we have seen, appears to exist dissolved in 

 plasma. I do not know what this special substance is ; it is derived 

 from the body separable by cold and also from leucocytes. I will 

 remark that it is not contained in ordinary serum, and hence is not 

 paraglobulin. 



Peptone plasma behaves in a totally different manner on 

 heating, according as it contains a considerable amount of the body 

 separable by cold or not. If this body be present, the plasma 

 remains, on heating to 56 — 57°, perfectly clear for a short time — ■ 

 five to fifteen minutes ; it then becomes gradually turbid, and finally 

 a dense flocculent precipitate forms ; but it is a very long time — 

 hours — before this precipitate reaches its maximum.* If it be absent, 

 the plasma does not give on prolonged heating to 56 — 57° any 

 coagulum, and remains perfectly free from any precipitate till a 

 very high temperature, 80 — 90°, is reached. It becomes opalescent 

 at high temperatures. In either case, whether the body separable 

 by cold be absent or present, the plasma, if mixed with an equal 

 quantity of 10 per cent, salt solution, remains free from any precipitate 

 till 80 — 90°, or higher, is reached. The upper limit varies somewhat, 

 often being as high as 95°. 



It must be understood that the precipitate mentioned above as 

 occurring in plasma at 56 — 57° may or may not contain the body 

 separable by cold, but it appears in very much larger quantity there 

 than does the latter, and represents the whole of the coagulable matter 

 of the plasma. It would therefore appear that in the process of heat- 

 ing, the same special body is liberated from the substance separable by 

 cold, as is the case when the latter is acted on by carbonic acid, i.e., a 

 body capable of converting the precursor of fibrinogen into fibrinogen 

 precipitable at 56°, and coagulable with fibrin ferment. The presence 

 of 5 per cent. NaCl prevents its development by means of carbonic 

 acid, and also by means of heat. 



In order not to obscure the point I have just been discussing, I 

 have left out of consideration the very small trace of true fibrinogen 

 pre-existent in peptone plasma. This was mentioned at the beginning 

 of the paper; it always separates on beating the plasma to 56", 

 whether it has been cooled or not, or whether salt be present or not, 

 but it is generally so very small in quantity that it is difficult to seo 

 the minute flocculi that separate at 56° ; hence the statements I mado 

 above as to the plasma remaining clear are practically correct. It 

 must not however be forgotten that in some rare cases, peptone plasma 

 # This slow clotting at 56-57° was observed by Fano. 



vol. xxxvnr. u 



