CHEMICAL COMrOSITIOX OF MUSCLE. 



121 



Fi- 80. 



pr. < 



proved this as regards the muscles of frogs. Two modes of production 

 of new fibres have been described — viz., firstly, from connective tissue 

 corpuscles lying between the existing fibres, by a 

 process analogous to the original development of the 

 muscle (von Wittich) ; secondly, by the splitting up 

 of a fibre throughout its whole length into two or 

 more smaller ones, preceded by multiplication of its 

 included nuclei. This second process has been de- 

 scribed by Weismann and by Kolliker as occurring 

 in frogs, in the winter season, and would appear to 

 serve for the replacement of fibres destroyed by fatty 

 degeneration, which is said to be not uncommon 

 in these creatures. Beale, however, denies that the 

 new and slender fibres are derived from a larger one 

 by splitting of its substance ; he believes that they 

 are produced from cells, as in the first mode, and 

 that the old fibre is removed. 



The great increase in the muscular tissue of the 

 uterus during gestation takes place both by elonga- 

 tion and thickening of the pre-existing fibre-cells of 

 which that non-striated tissue consists, and by the 

 development of new muscular fibre-cells from small, 

 nucleated, granular cells lying in tlie tissue. In the 

 shrinking of the uterus after parturition the fibre- 

 cells also diminish to their previous size; many of 

 them become filled with fat-granules (fig. 80), and 

 many are doubtless removed by absorption. 



As far as can be concluded from the observations 

 and experiments that have hitherto been made on 

 the subject, the striated muscular tissue is not re- 

 generated in warm-blooded animals. It is true that, 

 when a muscle is cut across, or a portion removed, 

 the breach will heal, but the loss of substance is not repaired by new- 

 formed muscular tissue. Striated muscular fibres have been found in 

 certain tumours of the ovary and testicle, but these cases are altogether 

 peculiar and abnormal. 



Fig. 80 — AIuscuLAR 

 Fibre-Cells from 



THE UtkRUS, 



THREE Weeks 

 AFTER Delivery, 

 treated with 

 Acetic Acid, mag- 

 nified 35(1 DIAME- 

 TERS (Kolliker). 



a, nuclei ; y, fat- 

 granules. 



COMPOSITION AND PROPERTIES OF MUSCULAR TISSUE. 



Chemical composition. — Muscular tissue contains nearly 80 per 

 cent, of water, so that in being dried it loses about four-fifths of its 

 weight. The chief and characteristic constituent of the fibre is an 

 albuminoid body. This was at one time regarded as fibrin ; ]jut, as 

 it was afterwards shown to be not identical with that substance, it 

 was distinguished by the name of syntoniii; the ground of distinc- 

 tion being, that syntonin is soluble in very dilute hydrochloric acid, and 

 can be extracted from muscle by that solvent ; also, that its solu- 

 tion is precipitated by neutral salts. More recently, the subject has 

 been investigated by Kiihne, who states that the albuminoid matter 

 of muscle exists in the fibres in a liquid form during life, but coagulates 

 after death, and thereby gives rise to the cadaveric rigidity which then 

 invades the muscles. When extracted from fresh and still irritable 

 frogs' muscles at a temperature of freezing, this substance, which 



