CHAP, ii.] THE CONTRACTILE TISSUES. 89 



hydrochloric acid, a large part of the material of the muscle passes, 

 as we have said, at once into syntonin. The quantity of syntonin 

 thus obtained may be taken as roughly representing the quantity 

 of myosin previously existing in the muscle. A more prolonged 

 action of the acid may dissolve out other proteids, besides myosin, 

 left after the washing. The portion insoluble in dilute hydro- 

 chloric acid consists in part of the gelatine yielding and other 

 substances of the sarcolemma and of the connective and other 

 tissues between the bundles, of the nuclei of these tissues and of 

 the fibres themselves, and in part, possibly, of some portions of 

 the muscle substance itself. We are not however at present in a 

 position to make any very definite statement as to the relation of 

 the myosin to the structural features of muscle. Since the dim 

 bands are rendered very indistinct by the action of 10 p.c. sodium 

 chloride solution, we may perhaps infer that myosin enters largely 

 into the composition of the dim bands, and therefore of the fibrillae ; 

 but it would be hazardous to say much more than this. 



57. Living muscle may be frozen, and yet, after certain 

 precautions will, on being thawed, regain its irritability, or at all 

 events will for a time be found to be still living in the sense that 

 it has not yet passed into rigor mortis. We may therefore take 

 living muscle which has been frozen as still living. 



If living contractile muscle, freed as much as possible from 

 blood, be frozen, and while frozen, minced, and rubbed up in a 

 mortar with four times its weight of snow containing 1 p.c. of 

 sodium chloride, a mixture is obtained which at a temperature 

 just below C. is sufficiently fluid to be filtered, though with 

 difficulty. The slightly opalescent filtrate, or muscle plasma as it 

 is called, is at first quite fluid, but will when exposed to the 

 ordinary temperature become a solid jelly, and afterwards separate 

 into a clot and serum. It will in fact clot like blood plasma, with 

 this difference, that the clot is not firm and fibrillar, but loose, 

 granular, and flocculent. During the clotting the fluid, which 

 before was neutral or slightly alkaline, becomes distinctly acid. 



The clot is myosin. It gives all the reactions of myosin obtained 

 from dead muscle. 



The serum contains an albumin very similar to, if not identical 

 with, serum albumin, a globulin differing somewhat from, and 

 coagulating at a lower temperature than paraglobulin, and which 

 to distinguish it from the globulin of blood has been called myo- 

 globulin, some other proteids which need not be described here, 

 and various ' extractives ' of which we shall speak directly. Such 

 muscles as are .red also contain a small quantity of haemoglobin 

 and possibly, another allied red pigment. 



Thus while dead muscle contains myosin, albumin, and other 

 proteids, extractives, and certain insoluble matters, together with 

 gelatinous and other substances not referable to the muscle 



