

GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 149 



Proteids obtained from , ParamyTsinogen ... . Te <^. 

 the dissolved clot . . I Myosinogen 550 ^ 



Proteids obtained from f Myoglobulin 63 o c 



muscle-serum . . . j Myo-albumin . ' 7 3 C. 



1 Myo-albumose (not coagulated by heat). 



The proteids of the serum can also be distinguished by their solubilities in 

 neutral salt-solutions of various strengths. The myoglobulin resembles serum- 

 globulin, although precipitated at 63 C. instead of 73 C. The myo-albumin 

 is apparently identical with serum-albumin. 



To these proteids we must add the pigment haemoglobin. Another pig- 

 ment, myohsematiu, is also found. It is not unlikely that these pigments have 

 here as elsewhere a respiratory function. 



Nitrogenous Extractives. -The chief nitrogenous extractive is creatin ; in 

 addition to this we find small amounts of creatinin and of various xanthin 

 bodies, as xanthin, hypoxanthin, carnin, and sometimes traces of urea, uric 

 acid, taurin, and glycocoll. The chemical nature of these bodies need not be 

 considered here. Physiologically they may be regarded as waste products 

 which result from the partial oxidation of the proteids of muscle during the 

 katabolic processes which are continually occurring even in the resting muscle 

 protoplasm. Monari has shown that the amount of creatin and creatinin is 

 increased by the wear and tear of muscular work, although the proteids of the 

 well-fed muscle probably supply but little of the energy which is set free. 1 



The non-nitrogenous constituents of muscle are fats, glycogen, inosit, sugar, 

 and lactic acid. 



Fats are usually found in intermuscular connective tissue, but there is little 

 within the normal fibre. It is doubtful whether fat plays any direct part in 

 the ordinary metabolic processes involved in the action of muscles, although 

 it is probable that if more available sources of energy are lacking it may, like 

 the proteids, be altered and employed. Under pathological conditions large 

 amounts of fat may be found inside the sarcolemma ; in phosphorus-poisoning 

 the degenerated muscle protoplasm may be replaced by fat in the form of fine 

 globules. 



Glycogen is found in very variable amounts in different muscles. The work 

 of many observers has shown that it is here, as in the liver, a store of carbo- 

 hydrate material, and is employed by the muscle, either directly or after con- 

 version into some other body, as a source of energy. The quantity, which is 

 rarely more than J per cent., lessens rapidly during muscle work. 



Sugar is found in muscles in small quantities only, nevertheless it probably 

 plays an important part, for Chauveau and Kaufmann,'by studying the levator 

 labii superioris of the horse, found that the muscles take sugar from the blood, 

 and that they take more during action than rest. The sugar which the mus- 



1 Fick und Wislicenns: Vierteljahresschnft der Ziiricher Naturforschenden Gesellsckafl, 1865, 

 Bd. x. p. 317 ; Pettenkofer und Voit : Zeitschrift fur Biologie, 1866, ii. ; Voit : Ibid., 1876, vi. 

 S. 305. 



