Lesson 19-1 The stuff of dreams
It is fairly clear that sleeping period must have some function, and because there is so much of it the function would seem to e important. Speculations about is nature have been going on for literally thousands of years, and one odd finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest. 'Rest', in terms of muscle relaxation and so on, can be achieved by a brief period lying, or even sitting down. The body's tissues are self-repairing and self-restoring to a degree, and function best when more or less continuously active. In fact a basic amount of movement occurs during sleep which is specifically concerned with preventing muscle inactivity.
stuff /stʌf/ 本质、 基本特征，特质，根本;
speculation /ˌspekjuˈleɪʃn/ 猜测;推测
literally /ˈlɪtərəli/ 真正地，确实地
odd /ɑːd/ 奇特的、古怪的，奇怪的
in terms of 从。。。方面看
tissue /ˈtɪʃuː/ (人、动植物细胞的)组织
restore /rɪˈstɔːr/ 修复; 恢复，使复原;
occur /əˈkɜːr/ 发生;出现;
specifically /spəˈsɪfɪkli/ 明确地;确切地说
concern /kənˈsɜːrn/ 与…有关;涉及;影响，
