We are so accnstomed ro standing upright as a natural attitude that few öf us think what a special complex raechanism is reqnired for this pnprose. A moment 's considerador) vrill show that the ordinary explanation of the erect position (the center of gravity to be clirectly above the f est) ia insniacient. When a man is suddenly shot, whether frorn the front .or behind, he drops on his face, for the truth is that there is mrcch more weight in the front of the spJDal colnmn than behiud it. The faot is that when -we are standing a large nnmber of povverfal masóles (both front and back) are simultaneously at work, the effects of their action being to neutraliza each other. Thrjs, the legs wou'd fall forward were it not that they are kept vertical en the feet by the strong tendón (the "Achules") at the back of tlie heel. At the same time the muscles of the thigh are tigbtened so asto prevent us taking a sitting position, and the ïnuscles of the back are pulled tense eo (bat the tronk does not stoop forvfard. The head is prevented from dropping on the chest by the ligaments in tbe nape of (he neck. That the npright is not its normal position is easily shown by the fact than a man nods as he is falling asleep, for as soon as the controlling nervons force is deadened tfie head drops forward by its own weight, oaly to be pulled back into position again with a jerk when the brain becomes stiddenly aware of an usual attitude.'