42 THEORIES OF COAGULATION. [BOOK I. 



with whose observations agree those made on the same subject by 

 Weyl and Hammarsten. Frederique has shewn that if an excised 

 jugular vein of the horse, tied so as to confine blood within it, be 

 heated to 56 C., a proteid matter separates, and the plasma is there- 

 after found to be uncoagulable. No better proof than this could be 

 given to shew that fibrinogen is really contained as such within the 

 living blood. Frederique has made use of the low temperature at 

 which fibrinogen coagulates to separate this body from paraglobulin 

 and determine its amount. He thus determined 100 grammes of 

 the plasma of the horse (in one experiment) to contain 0'4299 of 

 fibrinogen and to yield 0'375 grms. of fibrin. 



Theories of Coagulation. 



The views The first step in the accurate study of the nature of 



of the An- fa e coa g u l a ti on of the blood was made when it was 

 positively determined that coagulation is due to the 

 separation of a solid constituent from the liquor sanguinis, and this 

 fact was assuredly first determined with certainty by Hewson. It is 

 true that, as previously mentioned, Borelli had expressed himself 

 with correctness in the same sense ; still he did not adduce evidence 

 which can be considered to furnish full proof of his position 1 . 



Even before the discovery of this fact the cause of the coagulation 

 had been sought for, and various views had been expressed, none of 

 which, as even Hewson shewed, were at all capable of accounting for 

 the phenomenon. Thus it had been assumed by some that the 

 blood is maintained in a liquid condition in the living body by the 

 continual movement to which it is subjected (Borelli 2 , Lower 3 ); by 

 others, that coagulation was due to the action of air upon the blood ; 

 by a third set, that coagulation was due to the cooling of the blood 

 on its withdrawal from the vessels ; by a fourth, that the coagulation 

 of the blood was an act of life and connected with the vitality of the 

 blood (Hunter). The first of these views is contradicted by the 



1 See Borelli, De Motu Animalium. Opus posth., pars altera, 4to. Eoraae, 1681. Under 

 tlie heading "Analysis sanguinis in suas partes integrales, et forma compositionis ejus 

 inquiritur" (Prop, cxxxn.) Borelli says, "Deinde sicut in lacte adest succus con- 

 crescibilis in caseum, sic in sanguine reperitur succus viscosus, et glutinosus, qui post- 

 modum facta concretione, abit in fibras, vel membranas reticulares; quodque tales 

 fibrae sic condensatae non praeextiterint intra vasa animalis viventis, facile suadetur ex 

 eo, quod tales fibrae, et membranae albae sanguineae microscopio inspectae, crassiores 

 sunt vasis sanguineis capillaribus, et ideo neque excipi, neque effiuere in iis possint, 

 cum saltern longitudine filarnentorum, et latitudine membranarum, vias illas angus- 

 tissimas obstruerent. Ideo fatendum est, gluten album sanguiiieum lubricani et 

 nuidarn consistentiam retinere chim in animali viventi movetur." 



2 Borelli, op. cit., Vol. n. p. 266. 



3 Lower. The only passage in Lower's works which appears to the Author to indicate 

 that he entertained this opinion (which has been attributed to him) is the following : 

 "In cordis systole, qua liquor sanguinis conquassatur usque et ad ventriculi latera et 

 vasorum parietes alliditur, paululum diutius elanguescat: succus ejus nutritius in 

 partes secedere, grumescere, et gelatinae in modum incrassari, tandemque intra ribras 

 cordis hinc inde pendentes implicari, et ipsis ventriculorum parietibus accrescere, et a 

 cordis aestu indurari incipit, &c." Lower, De Motu Cordis. 



