Nor must the evident relation subsisting between fibrine and the sarcous tissue,
iu respect of their vital properties, be passed over in silence. In chemical constitu-
tion they may be said to be identical ; and there seems no doubt that muscle is
formed by the direct deposition in a solid form of the fluid fibrine of the blood, under
the elective attraction of the previously existing tissue. Now, in birds, the blood,
i.e., its fibrine, coagulates, or assumes the solid form, very quickly when it is with-
drawn from the vessels, in mammalia less so, and in reptiles and fishes very tardily,
if in these several cases it be placed in similar circumstances. A fatal stroke of
lightning, which instantaneously destroys contractility in the muscles, prevents also the
coagulation of the blood. In the same person, under health and disease, the blood
may vary much in the speed with which it coagulates, according to its chemical
constitution, the amount of oxygen accumulated in it, and the activity of the vital
processes ; and, after death, the coagulability of the blood, and the contractility of
the muscles, have a general correspondence, which has been even made the basis of ,
an hypothesis, ascribing the rigor mortis, or the dying act of contraction, to
coagulation of the blood." It will be subsequently explained t that the fibrine of the
blood, on becoming solid, acquires for a brief period the property of contractility ;
and this iu very different degrees, according to varieties in the same causes wliich
affect the speed of its coagulation. No one will pretend that this is not as much a
property of living fibrine when solid, as that of coagulating is of the same substance
when fluid ; and the correspondence between the coagulated living fibrine of the
blood and the living sarcous tissues in chemical constitution, in the possession of
contractility, and in the modea in which that vital property in both is affected by
similar causes, adds strong confirmation to the opinion we have expressed, that
contractility is a property of the living muscular substance as such.
