722 SPECIAL PHYSIOLOGY. 



the red corpuscles from the upper strata of the fluid, before coagula- 

 tion took place ; and this view is supported by the fact that the cor- 

 puscles, which are heavier than the liquor sanguinis, do subside in 

 blood, the coagulation of which is intentionally retarded by the addi- 

 tion of strong solutions of sulphate of soda or of common salt. But 

 other circumstances probably co-operate to increase the tendency of 

 the corpuscles to settle down. The disposition of the red corpuscles 

 to run together in columns and masses, in blood drawn from the body 

 and left at rest, is increased in the inflammatory state, the corpuscles 

 then running into larger clusters, clinging more firmly together, and 

 even losing their circular form, and becoming elongated. The aggre- 

 gation of the corpuscles into larger masses, perhaps causes them to 

 subside more rapidly than if they adhered in the usual minute piles or 

 columns ; and this, together with the retardation of the coagulating 

 process, may account for the formation of the buffy coat. This un- 

 usual aggregation of the corpuscles also occurs in certain low consti- 

 tutional states, and, it is said, in plethora ; it likewise happens, when 

 the coagulation of the blood is retarded intentionally in experiments. 

 A tendency of the corpuscles to fall to the lower part of a living vein 

 inclosed by ligatures, has been seen in animals. The nature and cause 

 of this tendency of the corpuscles to run together, remains, however, yet 

 unexplained. Their apparent mutual attraction is diminished by the 

 addition of weak saline solutions, and the buffy coat, if the blood be 

 inflammatory, is less distinctly developed, although the period of coagu- 

 lation is delayed. The addition of any material, which, like mucilage, 

 increases the aggregation of the corpuscles, accelerates the subsidence 

 of the corpuscles, and increases the buffy coat. 



Contrasting with the firm, fibrinous, and contracted clot of the 

 blood in inflammation, are the loose, soft coagula, characteristic of the 

 blood of weak, cachectic, and anaemic persons, even though the clot is 

 formed more rapidly. A deficiency of fibrin causes the clot to be soft. 

 During bleeding, the power of coagulation of the blood is gradually 

 modified as the blood flows, the last quantity drawn setting more rap- 

 idly, but forming a softer clot. Fragile, almost semifluid clots are 

 found in the blood of those who have died of cholera, from strokes of 

 lightning, or from asphyxia. 



That the immediate cause of the coagulation of the blood is the 

 solidification of the fluid fibrin of the liquor sanguinis, is shown by the 

 existence of the fibrinous fibrillse, in clotted, but not in fluid blood ; 

 by the formation of 'the buffy coat without any admixture of the red 

 corpuscles, the upper and firmest part of this coat being nearly pure 

 fibrin ; and lastly, by the fact that whipping the blood, which removes 

 the fibrin, prevents any further coagulation, the corpuscles themselves 

 not possessing this power, then remaining free and suspended, or sub- 

 siding in the serum, which is likewise no longer coagulable. Experi- 

 ments also demonstrate this property of the fibrin. Thus, if the coagu- 

 lation of the blood be retarded by the addition of solutions of neutral 

 salts, the red and white corpuscles have time to subside, and the upper 

 clear fluid, which still contains its fibrin, then undergoes coagulation, 

 the delicate colorless clot exhibiting the characteristic microscopic 



