MUSCLE. 



MUSCLE. 



990 



elements. The cross stripes of the fibre are formed, according to the 

 views of almost all the best observers of the day, by the apposition, 

 side by side, of the dark points seen on the separated fibrillje. That 

 they are not caused by a structure distinct from the nbrillse, and pre- 

 sent only on the surface of the fibre, is evident, according to Todd and 

 Bowman, from the following facts : 



1. That a transverse section of a Fibre shows it to be solid and not 

 hollow, and that the ends of the fibrillaj, as seen on ita section, exist 

 throughout its interior, just as on its surface. 



Fig. 2. 



Transverse section of three Elementary Fibres of the dried pectoral muscle of 

 a Teal, treated frith weak citric acid. 



2. That fibrilUc taken from any part of a fibre are marked with light 

 and dark poinU, corresponding in distance and force with the trans- 

 verse stripes of the fibre. 



3. That with a high magnifying power applied to a thick fibre we 

 may bring all parta of its interior into focus in succession, and 

 perceive throughout the same kinds of stripes. 



The Sarcolemina, or Tubular Sheath inclosing the striated fibre, 

 consists of a transparent, very delicate, but tough and elastic mem- 

 brane, which isolates the fibre from all other tissues. It most 

 commonly has no appearance of structure, but occasionally small 

 corpuscles, the remains of cell-nuclei are observed in it. 



Fig. 3. 



Fragment* of the Elementary Fibre of a Skate held together by nntorn but 

 twisted Sarcolcmma. 



If the fibre be immersed in acid, it swells, bursts the sheath, and 

 forma small protrusions or hernia;. 



The researches of Valentin and Schwann have thrown much light 

 on the development of muscular tissue in the embryo. In its earliest 

 stage, muscle consists of a mass of nucleated cells which first arrange 

 themselves in a linear series, and then unite to form the elementary 

 fibres. 



Fig. 4. 

 o ft e d B 



As the cells unite, a deposit of contractile material gradually takes 

 place within them. The deposition assumes a granular form, the 

 granular or sarcous elements being of the same size as in the perfect 

 muscle ; for this reason the transverse stripes resulting from their 

 apposition are of the same width as in the adult. Muscles grow by 

 an increase, not of the number, but of the bulk of their elementary 

 fibres. 



The Unstriped or Non-Striated fibres consist of modified simple 

 cells, usually fusiform, more rarely shorter and broader fibres, which 

 Kolliker calls " contractile or muscular fibre-cells." They are gene- 

 rally of a pale colour, bulged at intervals by oval or elongated cor- 

 puscles, or nuclei, which have frequently one or more nucleoli in 

 their centre (fig. 5). Their texture seems to be homogeneous. By 

 transmitted light they have usually a soft and very finely mottled 

 aspect ; their ordinary diameter varies from l-3000th to l-2000tU of 

 in inch. 



Fig. 5. 



Stages of Development of Striated Muscle Fibre. 



a, arrangement of the primitive cells in a linear scries. 



*, the cells united, the nuclei separated, and some broken up ; longitudinal 

 Hne becoming apparent. (From a foetal calf, three inches long.) 



c, it, transverse stripes apparent. In c the nuclei arc internal, and bulge the 

 flbre ; in rf they are prominent on the surface. (From a total calf, two months 



oil-) 



e, transverse stripes fully formed and dark ; nuclei disappearing from view 

 (From the human Infant *t birth.) 



/, elementary fibre from the adult, treated with acid, showing the nuclei 

 (from Schwann. The rest from Bowman.) 



Fibres of Unstriped Muscle. 



e, in their natural state ; a, treated with acetic acid, showing the corpuscles; 

 b, corpuscles or nuclei detached, showing their various appearajices. 



Muscular fibre is chemically distinguished from the fibre of cellular 

 tissue by the circumstance that it does not yield gelatin by prolonged 

 boiling in water, but dissolves in acetic acid, from which it may be 

 precipitated by ferrocyanide of potassium, showing that it belongs to 

 the protein-compounds. 



In consequence of the difficulty that exists in separating muscular 

 fibre from cellular tissue, vessels, and nerves, it is impossible to speak 

 with certainty respecting the behaviour of pure muscle towards 

 re-agents. If very small pieces of muscle are freed as much as possible 

 from fat and cellular substance, and immersed in water, blood, colouring 

 matter, and the extractive matter with which muscle abounds, are 

 gradually taken up, and colourless muscular fibres are left. 



Cold water and alcohol produce little effect on them, but in boiling 

 water they first contract and become firm, and subsequently soften. 

 Concentrated acetic acid dissolves them ; in the dilute acid they swell 

 and assume a transparent fibrous appearance. The alkaline carbonates 

 increase their firmness. Solutions of muscular fibre in dilute acids aro 

 precipitated by ferrocyanide of potassium and tannin in a precisely 

 similar manner to acid solutions of fibrin. Dried muscular fibre may 

 be easily pulverised ; in that condition it resembles the whole class of 

 protein-compounds in exhibiting strong positively electrical properties. 



On making incisions into the warm flesh of an animal Just killed, 

 we obtain by pressure an acid fluid which rapidly coagulates, in conse- 

 quence of the presence of a little fibrin : if the flesh has been kept 

 for some time, the fluid obtained by pressure no longer coagulates, 

 although it exhibits an acid re-action. No quantitative analysis of 

 human flesh has yet been made, but the flesh of several animals has 

 recently been submitted to analysis. The amount of water averages 

 about 80& and the greater part of the solid residue consists of fibrin ; 

 the other constituents, albumen, hsematoglobulin, fat, extractive 

 matters, lactic acid, the lactates, and other salts, occur in the expressed 

 juice. The proportions of these constituents have been determined 

 by Berzelius, Braconnot, Schlossberger, Schultz (and Marchand). In 

 the flesh of oxen they found : 



Berze- Bracon- Schloss- c . u Mar- 

 ,i.._ , ocnuuz. . ,. 



Water 



Fibrin, cells, vessels, and nerves 

 Albumen and hccmatoglobulin . 

 Alcohol-extract and Salts . 

 Water-extract and Salts . . 

 Phosphate of Lime with Albumen 

 Fat and Loss . . . 



lius. not. berger. ""' '" chand. 



77-17 77-03 77-60 77-50 76-60- 



17-70 17-18 17-50 15-00 18-00 



2-20 2-70 2-20 4'30 2'50 



1-80 1-94 1-50 1-32 1'70 



1-05 1-15 1-30 1-80 1-10 



0-08 traces O'lO 



_ _ _ 0-08 



100-00 100-00 100-00 100-00 100-00 



