52 TEXT-BOOK OF PHYSIOLOGY. 



Water, 73.5 



Proteins, including those of sarcolemma, connective tissue, 



pigments, 18 .02 



Gelatin, i .99 



Fat, 2.27 



Extractives, 0.22 



Inorganic salts, 3.12 (Halliburton.) 



When fresh muscle is freed from fat and connective tissue, frozen, rubbed 

 up in a mortar, and expressed through linen, a slightly yellow syrupy alkaline 

 or neutral liquid is obtained which has been termed muscle-plasma. This 

 fluid at normal temperatures coagulates spontaneously, the phenomena 

 resembling in many respects those observed in the coagulation of blood- 

 plasma. The coagulum subsequently contracts and squeezes out an acid 

 muscle-serum. The coagulated protein partakes of the nature of fibrin and 

 belongs to the class of globulins. Inasmuch as it is not present in living 

 muscle and only makes its appearance under conditions not strictly physio- 

 logic, it is regarded as a derivative of pre-existing proteins. An analysis of 

 muscle-plasma has shown the presence of at least two proteins which are 

 distinguished by their varying solubilities in different salt solutions, and by 

 the varying temperatures at which they coagulate. One of these proteins 

 coagulates at about 47 C. and because of its chemic relations has been 

 termed myosin or paramyosinogen; the other coagulates at about 56 C. 

 and for similar reasons has been termed myogen or myosinogen. The 

 latter is three or four times more abundant than the former. If the tempera- 

 ture of the cooled plasma be permitted to rise, both myosin and myogen 

 undergo a change of state termed coagulation. The substances resulting 

 are known as myosin fibrin and myogen fibrin. It is not known whether 

 these changes are due to the action of an enzyme or not. A similar change 

 in myosin ;and myogen occurs after death, giving rise to the condition known 

 as death stiffening or rigor mortis. The coagulation of these proteins in this 

 instance is probably caused by the presence and accumulation of metabolic 

 products. From the muscle-serum, according to Halliburton, may also be 

 obtained at 68 C. a globulin body termed myoglobulin and a small quantity 

 of myoalbumin. Among the proteins may be mentioned hemoglobin, which 

 gives the color to the muscles. Spectroscopic investigation reveals the 

 presence of a special pigment, myohematin, which is supposed to have a 

 respiratory function, inasmuch as its spectral absorption bands change by 

 oxidation and reduction. 



Among the extractives containing nitrogen may be mentioned creatin, 

 creatinin, xanthin, carnin, urea, uric acid, carnic acid, etc. Among the 

 extractives free of nitrogen, glycogen, dextrose, inosite, lactic acid and fat, are 

 the most important. Inorganic salts are relatively abundant, of which 

 potassium is the most abundant among the bases, and phosphoric acid 

 among the acids. 



THE PHYSICAL AND PHYSIOLOGIC PROPERTIES OF MUSCLE -TISSUE. 



Consistency. The consistency of muscle-tissue during life varies 

 considerably in accordance with different states of the muscle. In a state of 

 tension it is hard and resistant; in the absence of tension it is soft and fluctu- 

 ating to the sense of touch. Tension alone gives rise to hardness. 



