摘要：The author has already reported, applying the method of action current, on the function of each leg-muscle and the manner of movement of leg, dorsal and abdominal muscles in several different standing postures in detail (this Journal, Vol. 62, p. 21, p. 61). The muscles which influence the movement of shoulder joint were investigated, the results of which are as follows:A) Many descriptions have been made about the function of muscles for the movement of shoulder joint, using indirect methods, but the author's results obtained through direct method are different from theirs in the following points; a) m. trapezius pars transversea works when the scapula moves dorsalward, b) m. pectoralis major begins to work at the latter end of abduction, c) m. serratus lateralis does not work at internal rotation, but at external rotation, d) m. deltoides pars clavicularis does not work at abduction.B) The way of contraction of the muscles at the following several postures of upper extremities; a) ad- and abduction, b) lift of arm forward and backward, c) horizontal circumduction:- The curves which show the degrees of contraction of each muscle were figured. These figures can not be obtained by the existing indirect methods.C) The way of contraction of muscles at the normal standing posture.:- Of the muscles for movement of shoulder joint, m. trapezius pars descendens et transverse, m. deltoides pars spinata, m. supra spinam and m. rhomboides contract. Beside the muscles of shoulder joint, m. splenius capitis and m. semispinalis capitis are also contracting. And perhaps m. scalenus is working.D) The way of contraction of muscles in the hanging posture without power in shoulder :- In this case m. trapezius pars ascendens, m. latissimus dorsi, m. rhomboides, m. pectoralis major, m. serratus lateralis, m. deltoides, m. supra spinam, m. infra spinam and m. biceps et triceps brachii are contracting.E) The way of muscle contraction when the upper extremities is charged with a load (max.=40kg) (without power in shoulder):- M. trapezius pars descendens et transversa, m. deltoides, m. supra spinam increased their contraction in proportion to the weight of load. But m. biceps et triceps brachii does not work at all.F) The way of muscle contraction in walking:- Upon movement of upper extremities forward, m. trapezius pars descendens et ascendens, m. serratus lateralis, m. deltoides pars clavicularis, m. supra spinam and m. infra spinam are contracting, while backward, m. trapezius pars transverse, m. latissimus dorsi, m. deltoides pars spinata and m. supra spinam contract.
