CHAP. IL] THE CONTRACTILE TISSUES. 65 



is converted into coagulated proteid 1 , and it is worthy of notice 

 that it coagulates at a lower temperature, viz. 55 60 C., than 

 does serum-albumin, paraglobulin and many other proteids ; it is 

 precipitated and after long action coagulated by alcohol, and is 

 precipitated by an excess of sodium chloride. By the action 

 of dilute acids it is very readily converted into what is called 

 syntonin or acid-albumin 2 , by the action of dilute alkalis into 

 alkali-albumin. Speaking generally it may be said to be inter- 

 mediate 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 

 the myosin has thus been extracted by ammonium chloride solution, 

 little is known. If washed muscle be treated directly with dilute 

 hydrochloric acid, the greater part of the material of the muscle 

 passes at once into syntonin. The quantity of syntonin thus 

 obtained may be taken as representing the quantity of myosin 

 previously existing in the muscle. The portion insoluble in dilute 

 hydrochloric acid consists in part of the substance of the sarco- 

 lemma, of the nuclei, and of the tissue between the bundles, and in 

 part probably of certain structural elements of the fibres themselves. 



If living contractile frog's muscle, freed as much as possible 

 from blood, be frozen 3 , 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 coagulate like 

 blood-plasma, with this difference, that the clot is not firm and 

 fibrillar, but loose, granular and flocculent. 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 ordinary serum-albumin, one or more pe- 

 culiar proteids 4 coagulating at a lower temperature than does serum- 

 albumin, and extractives. Such muscles as are red also contain a 

 small quantity of haemoglobin, to which indeed their redness is 

 due. 



Thus while dead muscle contains myosin, serum-albumin, and 

 other proteids and extractives with certain insoluble matters and 

 certain gelatinous elements not referable to the muscle-substance 



1 See Appendix. 2 Ibid. 



3 Since, as we shall presently see, a muscle may be frozen and thawed again 

 without losing any of its vital powers, we are at liberty to regard the frozen muscle 

 as a still living muscle. 



4 See Appendix. 



F. 5 



