SKELETAL MUSCLE. 99 



effect of 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, the 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 C., has been obtained from all kinds of unstriped muscle. In a 

 muscular tumour of the uterus, Kossel 2 found the one coagulating at 

 45 C. (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-Eeymond 5 observed 

 in the stomach and intestines of birds that after death the muscular 

 walls were still alkaline. 



Myohcematin. Though haemoglobin is the pigment of the red 

 muscles, MacMunn 6 considers that the specific pigment of ordinary 

 muscle is myohamiatin, one of the most widely distributed of the colour- 

 ing matters which he has described under the name liistoluematins. The 

 histohsematins 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 haemochromogen ; and Levy, working under Hoppe- 

 Seyler, 7 has gone so far as to say that myohaematin is hsemochromogen 

 produced by the methods used to render the muscle transparent. The 

 resemblance is not absolute, but is specially close in what MacMunn calls 

 modified niyohaematin. 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 histohaeniatins 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 haemoglobin 

 as the source of the myohaematin ; whether this substance can be pro- 

 duced in the muscles intra mtam must be left to the future to decide. 9 



The extractives of muscle. These are (a) Nitrogenous, namely, 



Boruttau, Ztschr. f. physiol. Chem., Strasslmrg, Bd. xviii. S. 513. 



2 Quoted by Hoppe-Seyler, "Physiol. Chem.," S. 669. 

 Kiih 



3 Bernstein (Kiihne's "Lehrbuch," S. 332) found the actively contracting muscles of 

 Anodon acid. 4 "Lehrbuch," Bd. iii. S. 73. 



5 Monatsb. d. k. preuss. Akad. d. Wissensch. zu Berlin, 1859, S. 312. 

 G Phil. Trans., London, 1886 ; Journ. PhysioL, Cambridge and London, vol. vii. 



7 Ztschr.f. physiol. Chem. , Strassburg , Bd. xiii. MacMunn's reply is in the same vol. , S. 497. 



8 Halliburton, Journ. PhysioL, Cambridge and London, vol. vii. p. 325. 



9 K. Mb'rner (Nord. med. Ark., Stockholm, Festband, 1897) states that muscle pigment is 

 hemoglobin which spectroscopically shows slight differences from that obtained from blood. 



