PROTEIDS OF PLASM. I. 165 
As just stated, fibrinogen is precipitated from plasma, and from 
its solutions in neutral salt solution, or dilute alkalies, by the addition of 
dilute acetic acid, even in slight excess. This precipitate has been 
termed "thrombosin " by Lilienfeld, 1 who regards it as due to a splitting 
of the fibrinogen under the influence of the acid into this substance and 
an albumose, but it has not been shown that it pi any properties 
differing from fibrinogen.- 
From what has been stated, it will be seen that it is improbable that the 
material which is obtained from plasma, under the name of fibrinogen, is a 
simple substance. It is probably either a mixture, or a loose combination, of 
at least three substances, namely — 
1. Fibrinogen proper, coagulating at 56° C. 
2. The globulin described by Hammarsten, and termed fibrino-glooulvn\ 
coagulating at 65° C. 
3. A nucleo-prot< id. 
The nucleo-proteid of plasma. — Beyond the fact of its presence, and 
that it appears to be one of the essential factors in the formation of 
fibrin, very little is known regarding the nucleo-proteid of blood plasma. 
It is doubtful if it exists in the plasma of circulating blood ; it is 
thought by many that in this it is confined to the white corpuscles and 
blood platelets — a very little being also present in the red corpuscles — 
and that it is shed out by these as soon as the blood is drawn. The 
reasons for this belief are — 
1. White blood corpuscles and similar cells (lymph cells, thymus 
cells, etc.) always contain a considerable amount of nucleo-proteid. 
2. In plasma obtained by subsidence of the corpuscles there is most 
nucleo-proteid in the lower layers, which contain most leucocytes ; and 
least in the upper, which contain very few. 
3. Fluids which collect in the serous cavities of the body (peri- 
cardial thud, hydrocele fluid, ascitic fluid) frequently contain no 
leucocytes. "When this is the case they are also devoid of nucleo- 
proteid and of the property of sj>ontaneous coagulability, although they 
contain fibrinogen. 
The nucleo-proteid is precipitated from oxalate plasma, by allowing 
it to stand for twenty-four hours at 0° C. The addition of acetic 
in slight excess also throws it down, but not in a pure form, for fibrin- 
ogen is carried down along with it. Its solutions are coagulated at 65 C. : 
at a temperature of 60° C, in presence of free alkali, it is split into 
nuclein and a proteid. This is stated by Pekelharing to be a proteose, 3 
but its proteose character is denied by Martin. 4 Halliburton and Brodie 
could also find no proteose in blood after the injection of nucleo- 
albumin. 5 In the presence of soluble salts of lime, it forms a 
to justify this inference, and its presence is probably due to tbe fact that some or all of 
the nucleo-proteid present in the plasma is precipitated along with the fibrinogen, and 
clings to it in the subsequent processes of purification (Schafer, Proc. Physiol. Soc., Journ. 
Physiol., Cambridge and London, 1S95, p. xviii). See later, p. 172. 
1 Loc. cit. 
2 Schafer, Proc. Physiol. Soc, Journ. Physiol., Cambridge and London, 1895, vol. xvii. 
p. xx ; Hammarsten, Ztschr. f. physiol. Chem., Strassburg, Bd. xxii. S. 3S4 ; Cramer, ibid., 
1897, Bd. xxiii. S. 74. According to Hammarsten, this coagulum, like that produced in a solu- 
tion of the original fibrinogen, is not fibrin, but a fibrin-like combination of lime and fibrin- 
ogen. To me, however, it has often appeared difficult to distinguish from fibrin. 
3 Pekelharing, "Untersuch. 11. d. Fibrin-Ferment," Amsterdam, 1892. 
* Journ. Physiol., Cambridge and London, 1894, vol. xv. p. 375. 
5 Ibid., 1894-5, vol. xvii. p. 159. 
