CHAP. II.] THE BLOOD. 47 



Schmidt however soon proceeded a step further 1 . He studied the 

 effect of dilution upon, and the passage of carbon dioxide through, 

 liquor sanguinis and serum, and shewed how to obtain in this way, 

 though certainly not in a state of purity, the bodies which have been 

 described as paraglobulin and fibrinogen. He discovered that when 

 these bodies in a separate condition exist in solution and the 

 solutions are mixed, if. circumstances be favourable, coagulation 

 occurs sooner or later. 



These facts he explained by supposing that the formation of 

 fibrin is due to the inter-action of the two closely allied proteids, 

 of which the one, fibrinogen, is often present without the other, 

 paraglobulin; and to designate the property which the latter 



sesses of leading to the formation of fibrin from fibrinogen, 

 hmidt applied to it the name of the fibrinoplastic substance. 



Schmidt at first supposed that the plasma contained both fibrin- 

 generators in solution, there being, however, an excess of the fibrino- 

 plastic substance. When blood or plasma coagulates, he supposed 

 the whole of the fibrinogen to be used up, whilst the paraglobulin 

 over and above the quantity which had taken part in the formation 

 of fibrin, remained in solution in the serum, whence it could be 

 separated by dilution and neutralizing either with CO 2 or acetic acid. 

 Fluids which, like hydrocele, do not coagulate spontaneously, but only 

 after the addition of paraglobulin, he supposed to be wanting in this 

 body, which he regarded as one of the two essential fibrin- 

 generators. 



There are many ways of repeating Schmidt's observations on the 

 coagulating influence of paraglobulin on nbrinogen. One of the most 

 convenient is the following : the serum of blood is diluted, precipitated 

 by dilute acetic acid (10 c.c. of serum being diluted with 150 c.c. of 

 water and treated with four drops of 25 p. c. acetic acid). The precipitate 

 is washed with water. Eibrinogen is then precipitated (in an impure 

 condition) by saturating any fluid which contains it, e. g. hydrocele fluid, 

 with sodium chloride. The precipitate is collected on a filter, and after 

 the filtrate has passed through, the filter is filled up with water, which 

 dissolves the precipitated fibrinogen, in virtue of the sodium chloride 

 adhering to it. To this solution of impure fibrinogen the previously 

 precipitated paraglobulin is added, when coagulation sometimes occurs. 



Amongst the facts which were adduced by Schmidt and which 

 appeared to give great support to his views was this one : that if 

 from diluted plasma, the paraglobulin is precipitated by dilution of 

 water and passage of a stream of carbon dioxide, the power of 

 spontaneous coagulability is unquestionably destroyed, whilst it may 

 be occasionally restored by the restoration of the removed paraglobu- 

 lin to the fibrinogenous liquid. 



It is to be remarked that Schmidt never committed himself to a 



1 A. Schmidt, " Weiteres iiber den Faserstoff und die Ursachen seiner Gerimmng." 

 Archivf. Anat. u. Phijs., 1862, pp. 428469 and 533564. 



