MUSCLE. 95 
other cells present. The corpora lutea arc coloured by Lutein. This is a 
lipochrome (see p. 20). Thudichum l was the first to point out that it 
is distinct from haematoidin, which is also generally present. 
The constituents of eggs are described with the various proteins, 
etc., of which thcv are made up. 
Muscle. 
Skeletal muscle. — A muscle contains, besides the muscular fibres, 
supporting connective tissue with fat. Each fibre consists of two parts, 
the sheath or sarcolemnia, and the contractile substance which it 
encloses. The sarcolemnia resembles elastin very closely in its 
solubilities. 2 
The contractile substance is of soft consistency, and contains a large 
percentage of proteids, and smaller quantities of various extractives and 
salts. By the use of a press a juice can be squeezed out of perfectly 
fresh muscles, which is called the muscle plasma. Like blood plasma, 
this coagulates, and the proteid clot is called myosin ; this occurring 
within the body after death is the cause of rigor mortis. 
Living muscle is alkaline : but after extreme activity, and after 
death, the reaction becomes acid; this is due in part to the development 
of sarcolactic acid. 
The percentage of water in muscle varies in different animals : 3 — 
Man . 72 to 74 per cent. Birds . 70 to 76 per cent. 
Ox . .77 „ Amphibians 76 „ 80 ,, 
Pig. . 78 „ , Fishes . 79 „ 82 „ 
Cat . . 75 „ Crab . 85 „ 
Fox. . 74 „ 1 Pecten . 79 „ 80 „ 
greater. 
In young animals, and during inanition, the percentage of water is 
iter. 
Human muscle has the following average percentage composition : — 
Water 73-5 per cent. 
Solids 26-5 
Proteids, including sarcolemnia, proteids of con- 
nective tissue, vessels, and pigments . . 18-02 „ 
Gelatin 1-99 „ 
Fat 2-27 „ 
Extractives (creatine, lactic acid, glycogen, etc.) - 22 ,, 
Inorganic salts . . . . . . 3 -12 „ 
This may be compared with the muscle of a mollusc (Pecten) : 4 — 
Water 79-60 to 80-25 per cent. 
Solids ...... 
Proteids ...... 
Glycogen ...... 
Glycocine ..... 
Ethereal extractives .... 
Inorganic salts ..... 
1 Centralbl. /. d. mcd. Wissensch., Berlin, 1869. 
*-' Ewald, Ztschr. f. Biol., Miinehen, Bd. xxvi. S. 
3 Sehlossberger, " Chem. der Gewebe," Leipzig and Heidelberg, 1856, S. 169; Gorup- 
Besanez, " Lehrbueh," 1878, S. 676; Hoppe-Seyler, "Physiol. Chem.," S. 636. 
4 Chittenden, Ann. d. Chem., Leipzig, Bd. clxxviii. S. 266. 
20-40 
jj 
19-75 
15-68 
)> 
15-04 
2-43 
jj 
1-98 
0-71 
>> 
0-39 
0-33 
)) 
024 
1-26 
5> 
1-22 
Bd. vii. S. 
, 1. 
1. 
