CHAP, ii.] THE CONTRACTILE TISSUES. 97 



salt, preferably sodium chloride, and may be purified by being 

 washed with a saturated solution, dissolved again in a weaker 

 solution, and reprecipitated by saturation. Dissolved in saline 

 solutions it readily coagulates when heated, i.e. is converted into 

 coagulated proteid, and it is worthy of notice that it coagulates 

 at a comparatively low temperature, viz. about 56 C. ; this it will 

 be remembered is the temperature at which fibrin ogen is co- 

 agulated, whereas paraglobulin, serum-albumin, and many other 

 proteids do not coagulate until a higher temperature, 75 C. is 

 reached. Solutions of myosin are precipitated by alcohol, and the 

 precipitate, as in the case of other proteids, becomes by continued 

 action of the alcohol, altered into coagulated insoluble proteid. 



We have seen that paraglobulin, and indeed any member of 

 the globulin group, is very readily changed by the action of dilute 

 acids into a body called acid-albumin, characterised by not being 

 soluble either in water or in dilute saline solutions but readily 

 soluble in dilute acids and alkalis, from its solutions in either of 

 which it is precipitated by neutralisation, and by the fact that the 

 solutions in dilute acids and alkalis are not coagulated by heat. 

 When therefore a globulin is dissolved in dilute acid, what takes 

 place is not a mere solution but a chemical change; the globulin 

 cannot be got back from the solution, it has been changed into 

 acid-albumin. Similarly when globulin is dissolved in dilute alkalis 

 it is changed into alkali-albumin; and broadly speaking alkali- 

 albumin precipitated by neutralisation can be changed by solution 

 with dilute acids into acid-albumin, and acid-albumin by dilute 

 alkalis into alkali-albumin. 



Now myosin is similarly, and even more readily than is 

 globulin, converted 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 alkalis, 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, 



F. 7 



