SKELETAL MUSCLE. 
99 
effect nf numerous reagents, etc.) of myosinogen and paramyosinogen; (2) the 
influence of blood serum in hindering the coagulation of the muscle plasma ; 
and (3) the action of various chemical .substances on living muscle. 
Involuntary muscle. Our chemical knowledge of involuntary muscle 
is of a fragmentary nature. Like voluntary muscle, tin' heart becomes 
rapidly rigid after death, and simultaneously acid, 1 from the formation of 
sarcolactic acid. Both paramyosinogen and myosinogen are present in 
the muscle cells of the heart, and myosin is the result of coagulation. 
In the stomach and uterus, rigor has been observed, but in other forms 
of plain muscle it is difficult to recognise. A proteid coagulating at 
56 I '., has been obtained from all kinds of unstriped muscle. In a 
muscular tumour of the uterus, Kossel 2 found the one coagulating at 
45 0. (paramyosinogen) to be absent. 
The reaction of unstriped muscle is normally alkaline. 3 Lehmann 4 
found small quantities of lactic acid in the muscular substance of the 
stomach after death. There is, however, no marked change in the 
reaction after death, as in striated muscle. Du Bois-Reymond 5 observed 
in the stomach and intestines of birds that after death the muscular 
walls were still alkaline. 
Myohaematin. — Though haemoglobin is the pigment of the red 
muscles, MacMunn 6 considers that the specific pigment of ordinary 
muscle is myohaematin, one of the most widely distributed of the colour- 
ing matters which he has described under the name histohcematins. The 
histoha matins have only been observed by the spectroscope; they have 
not been separated out by chemical processes. They often occur in 
animals that possess no haemoglobin. As they undergo changes in their 
absorption bands, by oxygenation and reduction, it is believed that they 
are respiratory in function. The spectrum of these substances is some- 
what like that of fnemochromogen ; and Lev}', working under Hoppe- 
Seyler, 7 has gone so far as to say that myohaematin is haemochromogen 
produced by the methods used to render the muscle transparent. The 
resemblance is not absolute, but is specially close in what MacMunn calls 
modified myohaematin. This is produced by artificial gastric digestion ; 
or it can be obtained in the following way: — The muscle is chopped finely 
and covered with ether for some days. A yellow lipochrome derived from 
the fat between the muscular fibres 8 passes into solution, and below this 
floats a red juice, which on filtration gives the spectrum in question. 
Until myohaematin and the other histohaematins are examined 
by methods other than spectroscopic, it is impossible to pronounce 
positively on the point of dispute between MacMunn and Levy. The 
fact that in the last experiment described, the muscles, even if they are 
full of blood, yield no longer any haemoglobin, points to lnemoglobin 
as the source of the myohaematin; whether this substance can be pro- 
duced in the muscles intra vifam must lie left to the future to decide. 9 
The extractives of muscle. — These are — (a) Nitrogenous, namely, 
1 Boruttau, Ztsehr.f. physiol. C'hem., Strassburg, Bd. xviii. S. 513. 
- Quoted by Hoppe-Seyler, "Physiol. Chem.," S. 669. 
3 Bernstein (Ktthne's "Lelirbucb," S. 332) found the actively contracting muscles of 
Anodon acid. 4 " Lelirbucb," Bd. iii. S. 73. 
B Monatsb. d. k. preuss. Akad. <l. Jf'issensch. zu Br, ■Jin. 1S59, S. :.'.li!. 
,; Phil. Trans.. Loudon. 1886 ; Journ. Physiol., Cambridge and London, vol. vii. 
7 Ztsehr.f. physiol. < 'hem.. Strassburg, Bd. xiii. MacMunn 's reply is in the same vol., S. 497. 
s Halliburton, Jovrn. Physiol., Cambridge and London, vol. vii. p. 325. 
9 K. Morner (Kord. mud. Ark., Stockholm, Festband, 1897) states that muscle pigment is 
haemoglobin which spectroscopically shows slight differences from that obtained from blood. 
