CHAP. VII.] CONTRACTILITY OF MUSCLE. 189 



And it is extremely interesting to observe, that not only does a 

 less arterial character of the blood co-exist with a more enduring 

 contractility, but also that there is less of it supplied to the muscles, 

 for the above scale corresponds also with that in which animals are 

 ranged in regard to the size of the elementary fibres ; and we have 

 already seen that the vascularity of a muscle is inversely as the 

 thickness of its fibres. 



Thus we have animals ranged in the same series, whether we 

 estimate it by the duration of contractility, the degree of the 

 oxygenation of the blood and tissues, or the quantity of blood sent 

 to the muscles, viz., birds, insects, mammalia, reptiles, fish, and 

 Crustacea. The meaning of this correspondence may be further 

 illustrated by the phenomena of hybernation, in which all func- 

 tions are held enchained, and we are certain that nutrition proceeds 

 with extreme languor. In the hybernating animal, contractility is 

 very enduring, as compared with that property in the very same 

 organs when in a state of greater vital activity. 



Nor must the evident relation subsisting between fibrine and the 

 sarcous tissue, in respect of their vital properties, be passed over in 

 silence. In chemical constitution they maybe said to be identical; 

 and there seems no doubt that muscle is formed by the direct depo- 

 sition 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 quickly when it is withdrawn from the vessels, in mammalia less so, 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 contracti- 

 lity 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! that the fibrine of the blood, on becom- 

 ing solid, acquires for a brief period the property of contractility; 



* Orfila, BSclard, and Treviranus hold this view, which Miiller seems to 

 regard a,s not untenable, 

 t See chapter on the Blood. 



