THE BLOOD. 17 



seen numerous delicate fibres, the arrangement of which 

 may be compared to that of the needle-like crystals contained 

 in the solution of a salt in which crystallisation has com- 

 menced. Estimating, however, the coagulation neither from 

 its commencement nor from the complete formation and con- 

 solidation of the clot, but from the mean time between these 

 two points, it will generally be found that healthy blood 

 coagulates in from fifteen to twenty minutes. 



In diseased states of the system, however, the time occu- 

 pied in the coagulation of the blood, or, in other words, in 

 the formation of the crassamentum, or clot, varies very con- 

 siderably; and it is of much practical importance that the 

 principle which regulates this diversity should be clearly 

 understood. 



In disorders of an acute, active, or sthenic character, in 

 which the vital energies may be regarded as in excess, as, 

 for instance, in inflammatory affections, in pneumonia, pleu- 

 risy, acute rheumatism, and sanguineous apoplexy : in febrile 

 states of the system, as in the commencement of some fevers, 

 as in ague, plethora, and as in utero-gestation, the blood 

 takes a much longer time than ordinary to coagulate, no 

 traces of this change in the passage of the blood from a fluid 

 to a solid state being apparent until from sixteen to twenty 

 minutes have elapsed. This length of time may be accounted 

 for, by supposing that, in the affections named, the blood is 

 endowed with a higher degree of vitality, and that therefore 

 a longer period is required for its death to ensue; or, in 

 other words, if the expression may be allowed, that the blood 

 in such cases dies hard. On the contrary, in disorders of a 

 chronic, passive, or asthenic character, in all of which there 

 is deficiency of the vital powers, as in typhus, anemia, 

 chlorosis, the blood passes to a solid state in a much shorter 

 period than ordinary, even in from five to ten minutes. In 

 these cases the vitality of the blood is very feeble, and it 

 may be said to die easily. A remarkable difference is like- 

 wise observable in the characters of the clot formed in the 

 two classes of disorders named ; in the first it is firm, and 



c 



