124 THE HUMAN BODY. 



excitants, as electric shocks; that is to say, although the body 

 in general is dead and the beat of the heart and the flow of 

 blood have ceased, yet the muscles retain their vitality for a 

 while. This is especially the case with the muscles of cold- 

 blooded animals, as frogs and turtles, the muscles of wjiich 

 may, especially if kept cool, retain their living propertied for 

 several hours after removal from the body of the animal/ 



If muscles be taken in an early stage of rigor, rapidly^reed 

 as much as possible from tendons, fats and connective tissue, 

 and then finely minced and thoroughly washed with water, 

 most of the salts and crystallizable muscle ingredients eanjpe 

 dissolved away, along with a small amount of albumens; but by 

 far the greater part of the albumen is left behind in the form 

 of myosin, a proteid which is insoluble in water. On treating 

 the residue with a 10 per cent solution of ammonium chloride 

 the myosin dissolves and may be obtained as a flocculent 

 white precipitate by allowing the solution to fall drop by drop 

 into a large quantity of water, or by adding to it a consider- 

 able proportion of common salt. Myosin is related chemically 

 to fibrinogen and globulin, and its solutions in 10 per cent 

 neutral saline are coagulated by heat at the same temperature 

 (56 C. or 158 F.) as the former. 



Although myosin is apparently the least altered form in 

 which its chief proteid constituent can be separated from 

 muscle, it does not appear to exist, or at least exists in small 

 quantity if at all, in. living muscle; it is an early product of 

 post-mortem chemical changes. Its precursor in living muscle 

 has been named myosinogen, and a solution containing that 

 substance may be obtained as follows: Perfectly fresh and 

 still contractile muscles are cut out from a frog which has 

 just been killed by destruction of its brain and spinal cord, a 

 proceeding which entirely deprives the animal of conscious- 

 ness and the power of using its muscles, but leaves these lat- 

 ter unaltered and alive for some time. The excised muscles 

 are thrown into a vessel cooled below C. by a freezing mix- 

 ture and are thus frozen hard before any great chemical 

 change has had time to occur in them. The solidified mus- 

 cles are then cut up into thin slices, the bits thrown on a 

 cooled filter and let gradually warm up to the freezing-point 

 of water, after the addition of some ice-cold 0.5 per cent solu- 

 tion of common salt. Gradually a small quantity of a tena- 

 cious alkaline and transparent liquid filters through. This 



