154 THE BLOOD. 



and the fibrin accordingly coagulates. The escape of the am- 

 monia and of a certain quantity of the water of the blood aug- 

 ments this effect, and blood coagulates the sooner in proportion 

 as it is less watery. Coagulation within the blood-vessels he 

 regards as produced by the escape of some of the water of the 

 blood through the coats of the vessels. Some glutinous saps, as 

 that of the chara hispida (stone-wort), coagulate, like the blood, 

 chyle, and milk, and they all have albumen in the state of globular 

 precipitation and solution, have the same salts, and their coagu- 

 lation ceases when the solvent of the albumen is saturated, eva- 

 porated, or weakened. In sap, the solvent is acetic acid.P 



The fibrin may be separated from the red particles by agitation, 

 and in inflammatory diseases it very frequently separates when 

 drawn. Some conceive, that in health the cruor has a greater affinity 

 for fibrin than for the serum, and therefore unites with it in prefer- 

 ence. But to suppose any affinity of the red particles for either 

 the fibrin or the serum is erroneous. Leeuwenhoek and Hart- 

 soeker long since proved that serum merely suspends them; for if, 

 when separated, they are triturated in some serum, part of them 

 is taken up and the serum assumes a red colour; but, if the fluid 

 is allowed to settle in a cylindrical glass, they slowly precipitate 

 themselves to the bottom, and the serum above becomes clear 

 as before. When blood is drawn, the serum easily separates on 

 the coagulation of the fibrin. But the fibrin coagulates before 

 the colouring particles have time to fall to the bottom, and en- 

 tangling them acquires a red colour, forming the crassamentum : 

 if, however, the fibrin coagulates slowly and is thinner q, as in the 

 phlogistic diathesis and pregnancy, the greater specific gravity of 

 the cruor detaches it very considerably from the fibrin, which 

 remains colourless above, constituting what is called the inflam- 

 matory coat, crust, or buff. Berzelius even believes the fibrin 

 to be in a state of solution in the serum, while the cruor is simply 

 suspended in this solution. In the phlogistic diathesis both the 

 fibrin and the serum are more abundant, and the blood lighter. r 



Thinness of the blood and a disposition to slow coagulation 



Dr. Prout also says, " A portion of soda is requisite to preserve the weak 

 alcaline condition, essential to the fluidity of the blood." 1. c. p. 496. 



P 1. c. p. 372. sqq. 



*> Hewson, Experimental Enquiries into the J3lood and the Lymphatic System, 

 P. 1. p. 45. sq. 



r Scudamore, 1. c. 



