CHANGES IN THE BLOOD. 77 



far as it is known at present, exists only in the plasma of the 

 blood, of the Ijonph, and of the chyle, and in fluids derived 

 from them. 



" Coagulation of the blood " (says Professor Huxley) " is an 

 altogether physico-chemical process, dependent upon the pro- 

 perties of certain of the constituents of the plasma, apart from 

 the vitality of that fluid. This is proved by the fact that if 

 blood-plasma be prevented from coagulating by cold and greatly 

 diluted, a current of carbonic acid passed through it will throw 

 down a white powdery substance. If the white substance be 

 dissolved in a weak solution of common salt, or in an extremely 

 weak solution of potash or soda, it after a while coagulates, and 

 yields a clot of pure fibrin. It would be absurd to suppose that 

 a substance which has been precipitated from its solution, and 

 re-dissolved, still remains alive. 



" There are reasons for beheving that this white substance con- 

 sists of two constituents of very similar composition, which exist 

 separately in living blood, and the union of which is the cause 

 of the act of coagulation. These reasons may be briefly stated 

 thus : — The pericardium and other serous cavities in the body 

 contain a clear fluid, which has exuded from the blood-vessels, 

 and contains the elements of the blood without the blood cor- 

 puscles. This fluid sometimes coagulates spontaneously, as the 

 blood-plasma would do, but very often shows no disposition to 

 spontaneous coagulation. Wlien this is the case, it may never- 

 theless be made to coagulate, and yield a true fibrinous clot, by 

 adding to it a little serum of blood. 



" Now, if serum of blood be largely diluted with water, and a 

 current of carbonic acid gas passed through it, a wdiite powdery 

 substance will be thrown down ; this, re-dissolved in a dilute 

 saline, or extremely dilute alkaline solution, will, when added 

 to the pericardial fluid, produce even as good a clot as that 

 obtained with the original serum. 



" This white substance is called globulin. It exists not only 

 in serum, but also in smaller quantities in connective tissue, in 

 the cornea, in the humours of the eye, and in some other fluids 

 of the body. 



" It possesses the same general chemical properties as the 

 albuminous substance which enters so largely into the red 

 corpuscles, and hence at present bears the same name. But 



