THE LIVING ORGANISM 227 



knowledge may come to us in the reverse 

 order. 



With the development of the ovum of 

 higher plant or animal into its myriad brood 

 of different types of cells with correspondingly 

 different functions, the last great stage on our 

 journey of evolution is reached, and we have 

 now to consider some of the energy phenomena 

 which arise at this most complex stage of all, 

 on account of the life, or energy flux, lived 

 in common by these various nations of cells. 



The functions served by many of the great 

 systems of tissues of the body, and the 

 co-relationships of these to one another, are 

 so obvious as to require only passing mention. 

 There is the jointed osseous system of bones, 

 joints and ligaments which forms the skeleton, 

 and serves the purposes of preservation of 

 the form of the animal, locomotion, capture 

 and mastication of food, and the performance 

 of skilled manipulations of many kinds. 

 The osseous system is activated by the 

 voluntary muscular system, which in turn 

 is worked by the immense system of nerve 

 cells and their processes (the nerves) connected 

 with brain and spinal cord. Each apparently 

 simple voluntary movement such as those 

 of vision, eating, speaking or writing, is in 

 reality, as shown by Sherrington's researches, 



