EARLY ADVANCES IN THE MICROSCOPY OF MUSCLE

In the immediately preceding chapters attention has mainly been concentrated on the processes of energy provision for contraction; speculations concerned with the nature of the muscle machine itself were vigorously canvassed in the seventeenth century as we have seen, but it is necessary now to consider in detail the intensive work on this question which began early in the nineteenth century.

This work followed two main lines: first, the microscopic examination of muscle sections and fibres by ordinary and by polarised light; secondly, since the muscle structure must consist mainly of protein, the biochemical examination of the extracted proteins. Early in the twentieth century, the methods of X-ray diffraction were called upon, and about the middle of the century the phase contrast, interference and electron microscopes began to play their part. This chapter then, leading up to 1939 when Engelhardt & Lyubimova (1) made their pregnant discovery of the adenosinetriphosphatase activity of the structural protein myosin, will be concerned with the microscopic structure of the muscle machine and the nature of its protein composition.

After the first microsopic examination of muscle by Leeuwenhoek in 1674 and his discovery of the cross-striations in 1682, there was little progress for more than 100 years. This is to be correlated with the fact that during the eighteenth century, though much experimentation went on, no optical but only mechanical improvements were made in the microscopes generally available.