CHAP. IX.] THE CONTRACTILE TISSUES. 323 



The filtrate obtained by the above operation is a faintly yellow 

 opalescent liquid. It is muscle plasma. 



Properties Muscle plasma is of syrupy consistence ; it flows, 



of the muscle however, forms drops, and possesses all the characters 

 plasma. O f a liquid. It has a faint alkaline reaction. 



At ordinary temperatures muscle plasma coagulates exactly like 

 blood plasma. Coagulation is accelerated by contact with foreign 

 matter and commences at the points of contact ; it is also accelerated 

 by stirring with a glass rod. 



Myosin. 



The solid body which separates from muscle plasma when this 

 liquid coagulates has received the name of Myosin. This body differs 

 from fibrin in being a gelatinous mass when first formed, and though 

 it subsequently contracts, it never becomes fibrous, nor has the 

 opacity of blood fibrin. 



Reactions The separation of myosin is hindered by cold. At 



of muscle temperatures about 0C. it occurs very slowly, whilst at 



plasma de- 40 C. almost instantaneously. 



^S UP n When muscle plasma is diluted with cold water, 



myosin is instantly precipitated, so that a drop of 

 muscle plasma allowed to fall into water sets instantly in the form 

 of a solid elastic ball. Dilute acids, and solutions of NaCl containing 

 from 10 to 20 per cent, of the salt, cause instantaneous coagulation. 



Muscle plasma may be mixed with ice-cold salt solutions contain- 

 ing from 5 7 p.c. of NaCl without myosin separating. 



When plasma is allowed to flow guttatim into dilute hydrochloric 

 acid (containing 01 per cent.), the little balls which are at first 

 formed dissolve as they sink through the column of liquid, and give 

 rise to an opalescent solution. 



Pure myosin is obtained by dropping muscle plasma 



Prepara- ' n ^ ji^Hed water, whereby a precipitate consisting of 



myosin. little balls is obtained, which is easily washed with water. 



Myosin which has been thoroughly washed with water 



has a neutral reaction, is quite insoluble in pure water, but readily 



soluble in solutions of common salt containing between 5 and 10 per 



cent, of NaCl. 



Another method of preparing myosin is based upon the solubility 

 of coagulated myosin in weak solutions of common salt. Muscle 

 is thoroughly washed with water, is finely divided, and rubbed up to 

 the consistence of a fine paste with powdered common salt, the 

 amount of salt which has been added being determined. Water is 

 then added in such quantities as to form with the salt of the muscle 

 a solution containing 10 per cent, of NaCl. The mixture of finely 

 divided muscle, salt, and water, which should have the consistence of 

 a thin magma, is set aside for 24 hours, then pressed in linen, and 

 filtered through paper. The yellowish, syrupy, solution when poured 



212 



