548 PHYSICAL AND CHEMICAL PROPERTIES OF MUSCULAR TISSUE. 



The view expressed is supported by the following facts: (i) The analogy be- 

 tween the function of the muscle-substance and that of the contractile protoplasm 

 of cells, the latter surely possessing this semi-solid property, as must be inferred 

 from the movement of the protoplasm. (2) The observation of the course of the 

 contractile wave-movement through the length of the muscle-fiber. In the same 

 category belongs the wave-like movement first observed by W. Kiihne, when a 

 strong, constant current is passed through the muscle. The phenomenon depends 

 upon the occurrence of slow contraction-waves within the fibers in the direction 

 of the galvanic current, which are increased by heat, and disappear when the 

 muscle is tightly stretched, or when its extremities are forcibly pushed together. 

 (3) Under the microscope, the progression of a parasitic round-worm (Myoryctes 

 Weismanni) has been observed to fake place by means of the serpentine move- 

 ments through the contractile substance, the separated, semi-solid masses becom- 

 ing again confluent behind it. 



Refraction of Light. The contractile substance refracts the light doubly 

 (anisotropic) , while the ground-substance is singly refractive (isotropic). The 

 contractile substance behaves like a doubly refractive, positively uniaxial body, 

 whose optical axis corresponds with the longitudinal axis of the fiber. Under the 

 polarization-microscope, with the Nicol's prisms crossed and the fiber so placed 

 that the longitudinal axis intersects the vibration-planes of the Nicol's prisms 

 at an angle of 45, the doubly refractive substance can be recognized by its ap- 

 pearing bright in a dark field of vision, while in a colored field (purple-red from 

 the interposition of a mica plate) it appears of another color (blue, yellowish-red, 

 to yellow). Although the doubly refractive contractile substance undergoes 

 change in form during contraction, its double refraction nevertheless persists 

 unaltered. Catherine Schipiloff, A. Danilewsky, and O. Nasse believe that the 

 contractile, anisotropic mass consists of myosin. According to the observations 

 of Engelmann all contractile elements possess the property of double refraction, 

 and the direction of shortening always corresponds with that of the optical axis. 

 With respect to the actual cause of the anisotropy, the comprehensive investiga- 

 tions of v. Ebner have demonstrated that as a result of the processes of growth 

 in the tissue, tensions are produced (for example, the tension-phenomena of bodies 

 subject to imbibition) that give rise to double refraction. 



During sustained contraction in degenerating muscle-fibers the refractive index 

 of the muscle-substance is increased as a result of loss of water from the tissue 

 and the consequent increased concentration of the dissolved parts of the muscle. 



The chemical composition of muscle undergoes rapid and profound 

 changes after death. As, however, the muscles of the frog, when thawed 

 after freezing, again become capable of contracting, they are, therefore, 

 not altered chemically by the freezing. W. Kiihne cooled to 10 C. frogs' 

 muscles rendered bloodless by means of a i per cent, sodium-chlorid 

 solution, triturated them in an ice-cold mortar, and expressed the juice 

 (which thaws at 3) through linen. The fluid thus expressed is filtered 

 in the cold and appears as a slightly opalescent juice of a neutral or 

 generally alkaline reaction and light yellowish tint, and designated 

 muscle-plasma. In common with blood-plasma it coagulates spon- 

 taneously. The muscle-plasma becomes at first uniformly gelatinous. 

 Later, turbid, opaque, doubly refractive flakes and threads undergo con- 

 traction in the jelly, and like the fibrin of the contracting blood-clot 

 express a juice, muscle-serum, which has an acid reaction. Cold prevents 

 the coagulation of muscle-plasma; above o it takes place but slowly, 

 then more rapidly with increasing temperature, finally with great rapidity 

 at 40 C. for the muscles of cold-blooded animals, or at 55 C. for those 

 of warm-blooded animals. The addition of water or of a little acid to 

 the muscle-plasma causes immediate coagulation. This coagulated 

 proteid, the most abundant in the muscles, is derived from the doubly 

 refractive substance, and is designated myosin. Its chemical formula 

 is C 108 H 172 N 30 S0 33 . 



Myosin forms from 3 to n per cent, of moist muscular tissue. It can be 



