SKELETAL MUSCLE. 97 
does cold prevent the coagulation of muscle plasma, but, as in the case of 
blood plasma, admixture with solutions of neutral salts has the same 
effect. Addition of water to the salted muscle plasma brings about 
coagulation (an acid reaction making its appearance simultaneously), 
especially at 40° C, and still more rapidly it' solution of "myosin 
ferment" is added. The myosin ferment was prepared from muscle 
in the same way as fibrin ferment from blood serum. 
Saline extracts of muscle which has undergone rigor mortis, resemble 
salted muscle plasma very closely; after dilution they undergo coagula- 
tion; this may be a re-coagulation of the redissolved myosin, for the 
acidity of the saline extract is increased by re-coagulation. Some 
observers, however, regard this phenomenon not as a true re-coagulation, 
but as a simple precipitation of the myosin by dilution with water. 
Myosin may be most readily extracted from muscle by means of 
ammonium chloride solution, and may be precipitated in a gelatinous 
form by dialysing away the salt. 1 Elementary analysis 2 gives the 
following results :— C\ 52-79; H, 712; N, 16-80: S, 1'26; 0, 22-97. 
Eecent research has shown that calcium salts are essential for the 
effective coagulation of milk and blood. The facts are not so positive 
in the case of muscle, but there is some evidence pointing to the 
existence of an analogy in the three cases. 3 
By fractional heat coagulation, and by their varying solubilities in 
different salts, I was able to separate four different proteids in the 
muscle plasma. 
(1) A globulin precipitable by heat at 47° C. This is analogous to 
the cell globulin found in most protoplasmic structures. It is termed 
musculin by Hammarsten. I gave it the name paramyosinogen. 
(2) A globulin precipitated by heat at 56° C. This is the proteid 
which is especially acted on by the myosin ferment, and is converted 
into myosin. I termed it myosinogen: both it and paramyosinogen 
contribute to the muscle clot. 
(3) A third globulin precipitated at 63° C. (myoglobulin) is con- 
tained in the muscle serum. 
(4) Small quantities of an albumin (myoalbumin), similar in its 
properties to serum albumin, are also present. 
In addition to this, in the case of red muscles, there is haemoglobin ; 
and if the muscle has been kept warm, and acidity developed, small 
quantities of proteoses and peptone, which are formed by a process of 
self -digestion. Briicke showed, many years ago, that muscle contains 
small quantities of pepsin, doubtless absorbed from the gastric mucous 
membrane ; tliis becomes active on the onset of acidity. The action of 
such a ferment within the body will perhaps explain the phenomenon 
called the disappearance of rigor mortis; it is unnecessary to suppose 
that this is always due to putrefactive organisms, 4 since rigor often dis- 
appears before putrefaction sets in. Perfectly fresh muscle contains no 
proteose or peptone. 5 
Whitfield also investigated the question whether myosin or its precursors are 
1 Kiihne and Chittenden, Ztsclir.f. Biol., Miinchen, Bd. xxv. S. 35S. 
2 Chittenden, ibid. See also Stud. Lab. Physiol. Chan., New Haven, 1S89, vol. iii. 
p. 116. 
3 Locke, Journ. Physiol., Cambridge and London, vol. xvii. p. 293 ; other references will 
be found in this paper. 
4 Cossar Ewart, Proc. Physiol. Soc, London, 1887, p. xxv. 
5 Whitfield, Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 487. 
VOL. I. — 7 
