UNSTRIATED MUSCLE TISSUE. 475 



mortis. The electrical changes are, however, very transitory, 

 and are followed by complete loss of elasticity and irritability. 

 Opacity of the tissue accompanies its later stages. 



Thus, while dying, the muscle tissue may be said to go through 

 a series of events analogous to those which would occur in a pro- 

 longed contraction without any period of recuperation. The idea 

 naturally has suggested itself to the minds of physiologists that 

 the active state of muscle depends upon chemical changes which 

 are the initial steps in the coagulation of the contractile substance, 

 when the muscle is dying. The muscle tissue is supposed to con- 

 tain a special proteid of extremely intricate and unstable chemical 

 constitution, which, like all plasmata, is constantly undergoing 

 slow molecular change, and which, if not reintegrated by constant 

 assimilation, would pass into coagulation. Under the influence of 

 stimuli a comparatively sudden and intense molecular disturbance 

 is brought about, which produces shortening of the fibres and 

 the same chemical changes as precede the coagulation. Before 

 the stage of coagulation appears, however, a chemical rearrange- 

 ment takes place, the result of which is the reconstruction of the 

 unstable complex proteid. If nutriment be withheld, or if the 

 stimulation be too powerful, the recovery cannot take place, and 

 we find the muscle passing from a state of physiological contrac- 

 tion to one of intense exhaustion, and then to coagulation and 

 death. 



UNSTRIATED MUSCLE. 



So far reference has only been made to the skeletal muscles, 

 the fibres of which are marked by transverse striations, and 

 whose single contraction is extremely rapid and short. The con- 

 tractile tissues which carry on the movements in the various 

 organs of the body are not striated fibres, but, as has been already 

 stated, consist of elongated flattened cells with rod-shaped nuclei. 

 They occur generally in the form of sheets or layers forming 

 coats for the organs in which they lie. Their single contraction 

 is slow and prolonged, and commonly is transmitted from one 

 muscle cell to another as a kind of sluggish wave. They are in- 



