302 



ABSORPTION AND SANGUIFICATION. 



an abnormal degree ; or such as have found their way into it from 

 without. Thus, Carbonic Acid, Urea and Lithic Acid, Cholesterine 

 and other elements of Bile, and other matters which it is the office of 

 the Excreting organs to remove, may accumulate in the blood, and 

 may become fertile sources of disease, by their injurious influence. 

 The introduction of various Mineral substances, by absorption from 

 without, changes the composition of the normal elements of the Blood, 

 and thus affects their vital properties ; thus strong saline solutions 

 diminish or destroy the coagulating power of the Fibrine. But the 

 most remarkable cases of depravation of the Blood, by the* introduc- 

 tion of matters from without, are those which result from the action of 

 ferments, exciting such Chemical changes in the constitution of the 

 fluid, that its whole character is speedily changed, and its vital pro- 

 perties are altogether destroyed. Of such an occurrence we have a 

 marked example in the various forms of malignant fevers ; in which 

 the introduction of a very minute quantity of noxious matter into the 

 blood, either through the lungs or through the skin, produces a speedy 

 alteration in the characters of the whole mass of the blood, the func- 

 tion of every organ in the body is disordered, and decomposition of 

 the solids and fluids takes place to a considerable extent, even before 

 the circulation ceases, and whilst consciousness yet remains. The 

 train of symptoms produced by the bite of venomous Serpents, and of 

 rabid animals, appears referable to the same cause, the alteration in 

 the condition of the whole current of blood, by the introduction of a 

 minute quantity of a substance that acts as a ferment. 



535. The Coagulation of the blood, as already explained, depends 

 upon the passage of its Fibrine from the fluid state to the solid ( 184); 

 consequently, if the Fibrine be separated from the other elements, no 

 coagulation takes place. On the other, hand, if the amount of Fibrine 

 be larger than ordinary, the coagulum possesses an unusual degree of 

 firmness. The length of time which elapses before coagulation, and 

 the degree in which the Clot solidifies, vary considerably ; in general 

 they are in the inverse proportion to each other. Thus, if a large 

 quantity of blood be withdrawn from the vessels of an animal at the 

 same time, or within short intervals, the 'portions that last flow coagu- 

 late much more rapidly, but much less firmly, than those first obtained, 

 in consequence of the diminished proportion of fibrine. On the other 

 hand, when the fibrine is in excess, its coagulation is unusually de- 

 layed. From this delay an important change results, in the mode in 

 which the coagulation takes place ; for the red corpuscles, instead of 

 being uniformly diffused through the coagulum, have time to sink to the 

 bottom, in virtue of their greater specific gravity ; and the upper part 

 of the clot is consequently made up of Fibrine, almost exclusively, 

 whilst the lower is chiefly formed by the aggregation of the red cor- 

 puscles. Hence the upper layer is almost destitute of colour (whence 

 it has received the name of huffy coat), and is remarkably tenacious in 

 its character ; whilst the lower is very deep in hue, and very friable in 

 consistence. When the fibrillated network forming the buffy coat 

 undergoes the slow contraction, which is characteristic of highly-elabo- 



