CHANGES IN A MUSCLE DURING CONTRACTION. 85 



min. Similarly when globulin is dissolved in dilute alkalies it is changed 

 into alkali-albumin ; and, broadly speaking, alkali-albumin precipitated by 

 neutralization can be changed by solution with dilute acids into acid-albu- 

 min, and acid-albumin by dilute alkalies into alkali-albumin. 



Now myosin is similarly, and even more readily than is globulin, con- 

 verted into acid-albumin, and by treating a muscle, either washed or not, 

 directly with dilute hydrochloric acid, the myosin may be converted into 

 acid-albumin and dissolved out. Acid-albumin obtained by dissolving 

 muscle in dilute acid used to be called syntonin, and it used to be said that 

 a muscle contained syntonin ; the muscle, however, contains myosin, not 

 syntonin, but it may be useful to retain the word syntonin to denote acid- 

 albumin obtained by the action of dilute acid on myosin. By the action of 

 dilute alkalies, myosin may similarly be converted into alkali-albumin. 



From what has been above stated it is obvious that myosin has many 

 analogies with fibrin, and we have yet to mention some striking analogies ; 

 it is, however, much more soluble than fibrin, and, speaking generally, it 

 may be said to be intermediate in its character between fibrin and globulin. 

 On keeping, and especially on drying, its solubility is much diminished. 



Of the substances which are left in washed muscle, from which all the 

 myosin has been extracted by ammonium chloride solution, little is 

 known. If washed muscle be treated directly with dilute 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 hydrochloric acid consists in part of the gelatin-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 them- 

 selves, 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 

 a 10 per cent, sodium chloride solution, we may, perhaps, infer that myosin 

 enters largely into the composition of the dim bands, and, therefore, of the 

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



60. 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 per cent, 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 afterward separate into a 

 clot and serum. It will, in fact, coagulate like blood-plasma, with this dif- 

 ference, that the clot is not firm and fibrillar, but loose, granular, and floc- 

 culent. During the coagulation 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 



