A text book of physiology / by William Rutherford.

Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: A text book of physiology / by William Rutherford. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    148/180 (page 136)
    13G the periphery inwards. When this has proceeded to some extent a fibre of mammalian striped muscle is a tube of fibrils enclosing a core of uudiiferentiated protoplasm with many nuclei. But as development pro- ceeds, the nuclei, with some protoplasm, leave the centre and appear at the peripheiy of the fibre. Probably they move outwards in the spaces between the fibrillar bundles. But in the striped muscle of the frog the nuclei are at an early period of development all placed outside the striated substance. Many of them continue there as the nuclei under the sarcolemma, whilst some of them appear to move into the interior of the fibre and remain permanent between the fibrillar bundles (Ranvier, Op. 39, 515). With regard to the origin of the sarcolemma of stri])ed muscle, all are agreed that it does not exist at an early stage in the development of the fibres, but its mode of forma- tion is disputed. Kblliker regards it as nothing but a cell-membrane produced around the protoplasm. This idea is supported by tlie observations of Wilson Fox {Op. 3, year 1866), and by Calberla {Op. 24, iv. 111). Wolft' {Op. 24, vi. 101), however, reganis it as a transformation of special cells which disappear in the process. It must not, how- ever, be foigotten that the muscle-corpuscles may be readily mistaken for such cells, and that in the case of non-striped muscle—where there are no peripherally placed muscle-corpuscles, there is no evidence of the production of the sarcolemma from special cells. Probably in both cases the sarcolemma is merely a cell-membrane. The fibres of striped muscle are also developed after embryonic life has ended. Much of the enlargement of growing muscles is due to an increase in the number of the fibres, but the origin of the new fibres still requires elucidation. Their development is to be seen in the frog during the spring time, when those striped fibres which have w-astcd during the winter are replaced by new ones. Two modes of development are described—1. Weismann and Kolliker state that new fibres result from a longitudinal cleavage of the old ones. 2. According to Von Wittich they spring fro7n connective tissue corpuscles. In the testis and ovary, where tumours of striped muscle sometimes, though rarely, arise, connective tissue corpuscles, or at all events blood-leucocytes, appear to be their source. It is commonly stated that when striped muscle is destroyed it is not regenerated in warm-blooded animals, and that when cut across or partly removed the breach is healed, not by new muscle, but by fibrous tissue. In a recent research, Kraske {Op. 24, vii. Ab. i. 75), working under the direction of Cohnheim, has shown that when the striped muscle of the rabbit is cauterised by the interstitial injection of carbolic acid, no fibrous cicatrix appears at the cauterised spot, but in the course of six weeks it is filled up with newly developed muscle. He finds that the earcous substance of the old fibres disappears, the liiuscle-corpuscles proliferate and grow spindle-shaped. The sarcolemma vanishes, and the liberated muscle-corpuscles severally become striped fibres. In a growing muscle there is not only an increase in the number of the fibres, but the individtial fibres grow larger; thus, the striped fibres of the adult are longer and about five times broader than those of the newly- born child. According to Frey, the enlargement is due to interstitial growth. This theory seems to hold in the case of the growing non-striped fibres of the jn-egnant uterus, and probably it also to some extent holds as to those of striped muscle, but there is certainly another way in which the latter grow. The nuclei under the sarcolemma multiply, the proto- plasm around them increases in quantity, and is converted into sarcous matter. This mode of growth may be seen in many of the fibres of the diaphragm of young and also of adult mammals (Klein, Op. 69, p. 80). A similar change takes place in striped muscle elsewhere, when it is sub- jected to prolonged and systematic exercise.