538 THE THIRD HUXLEY LECTURE 



might be explained by some drying on account of the imperfect fitting of the cap. 

 The fluid part of the blood soon coagulated. 



The result of this experiment seemed to me of itself sufficient evidence 

 that the blood requires no action of the Hving vessels to maintain its fluidity, 

 and that the hypothesis of such action was superfluous. 



At the same time the extreme care required in order to ensure the success 

 of such an experiment indicated the subtilty of the influence of an ordinary 

 solid in bringing about coagulation. A very simple experiment, performed 

 in a butcher's establishment on the way from my father's house at Upton to 

 deliver the Croonian Lecture before the Royal Society, illustrates the same 

 thing. I received blood from the throat of an ox into two similar open earthen 

 jars (galhpots), and slowly moved a clean glass stirring-rod through the blood 

 of one of them for a second or two, and then left both vessels undisturbed. 



In the course of a few minutes the blood that had been thus gently and 

 briefly stirred was a mass of coagulum, while the unstirred blood was still fluid, 

 except a thin layer of clot encrusting the wall of the jar. In course of time 

 it also coagulated completely. Now we know, from the experiment with the 

 ox's jugular, that coagulation is propagated with extreme slowness, if at all, 

 from a clot in blood perfectly undisturbed. The earlier coagulation of the 

 main mass of the stirred blood was, therefore, not caused by propagation of 

 the process from a layer upon the surface of the jar, but must have been the 

 result of the brief agency of the glass rod. 



A little before the delivery of the lecture referred to,^ I became aware of 

 the recent very important observations of Schmidt, who showed, as had been 

 foreshadowed many years previously by Andrew Buchanan, of Glasgow, that 

 normal liquor sanguinis does not, as had been supposed, contain fibrine in solu- 

 tion but only one constituent of that substance, termed by Schwann fibrinogen, 

 the other constituent being derived from the blood-corpuscles. The ordinary 

 solid, therefore, in determining coagulation, does not cause the deposition of 

 fibrine already formed, but so influences the corpuscles as to make' them give 

 up an ingredient necessary for the formation of that insoluble body.^ 



With this further light upon the subject, the conclusions derived from the 

 experiments to which I have referred seem to explain the special coagulability 

 of the exudation in intense inflammation. Under intense irritation the capillary 

 walls will naturally be affected by the noxious agency as the veins of the sheep's 



* Vide the Croonian Lecture, ' On the Coagulation of the Blood,' Proceedings of the Royal Society, 1863 

 (reprinted in vol. i, p. 109). 



^ Regarding the corpuscular elements of the blood which are concerned in supplying to the plasma 

 the materials necessary for the formation of the fibrine and the chemical interactions of those substances, 

 various important researches have since been conducted, in which I have had no share. 



