A text book of physiology . t about its middle, where the nerve ends in an end-plate,and the contraction wave starting from the end-plate travels alongthe muscular fibre in both directions. In such a case therefore, stillmore even than in the urarised muscle stimulated artificially at oneend, must the whole fibre be occupied at the same time by the waveof contraction. Changes in microscopic structure. When portions of livingirritable muscle are examined under the microscope, contraction 1 Untersuch. u. d. Erregungsvorgang im Nerven- unci Musltelsysteme, 1871, p. 84. 2 Pflugers Archiv, x. (i875
A text book of physiology . t about its middle, where the nerve ends in an end-plate,and the contraction wave starting from the end-plate travels alongthe muscular fibre in both directions. In such a case therefore, stillmore even than in the urarised muscle stimulated artificially at oneend, must the whole fibre be occupied at the same time by the waveof contraction. Changes in microscopic structure. When portions of livingirritable muscle are examined under the microscope, contraction 1 Untersuch. u. d. Erregungsvorgang im Nerven- unci Musltelsysteme, 1871, p. 84. 2 Pflugers Archiv, x. (i875) 48. 3 Archiv /. Anat. u. Phys., 1875, p. 526, Chap, il] THE CONTRACTILE TISSUES. 53 waves similar to those just described, but feebler and of shorterlength, may be observed passing along the fibres. By appropriatetreatment with osmic acid or other reagents, these short contractionwaves may be fixed, and the structure of the contracted portion com-pared at leisure with that of the portions of the fibre at rest. In Fig. 10,. Fig 10. Muscular fibre undergoing contraction. The muscle is that of Telephoras melanurus treated with osmic acid. The fibre at cis at rest, at a the contraction begins, at b it has reached its maximum. The rightband side of the figure shews the same fibre as seen in polarized light. (AfterEngehnann.) representing a fibre of the muscle of an insect (in which these changescan be more satisfactorily studied than in vertebrate muscle), the con-traction wave begins near a, and has reached about its maximumat b, while at c the fibre is at rest, the contraction wave not havingreached it (or having passed over it, for the beginning and end of thewave are exactly alike). It will be seen that at b, each disc of thefibre is shorter and broader than at c. Further, while at c the dimband x is conspicuous, and the light band y, with its accessorymarkings y, is together lighter than the dim band x, at b in the fullycontracted part of the fibre the dim band appears light
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