1. Telemetering electromyography has been used to investigate the pattern of activity of certain muscles of the lower limb and back while the subjects walked up and down stairs.

2. During walking up and down stairs each limb has a supporting and swinging phase in each complete step.

3. Walking up stairs revealed the following facts. Firstly, raising the body on to the stair above is brought about by the contraction of the soleus, quadriceps femoris, hamstrings and gluteus maximus; the gluteus medius at the same time prevents the body falling on to the unsupported side. Secondly, the tibialis anterior dorsiflexes the foot during the swinging phase and helps the limb to clear the stair on which the supporting limb is placed. Thirdly, the hamstrings flex the leg at the knee in the early part of the swinging phase and control the terminal part of extension at the knee at the end of this phase. Fourthly, both erectores spinae contract twice in each step and control the forward bending of the body at the vertebral column.

4. Walking down stairs revealed the following. Firstly, the body is lowered on to the stair below by the controlled lengthening of the soleus and quadriceps femoris; the gluteus medius at the same time prevents the body from falling on to the unsupported side. Secondly, the tibialis anterior inverts the foot at the beginning of the supporting phase as the toe is placed on the stair below and dorsiflexes the foot in the middle of the swinging phase. Thirdly, the hamstrings control the extension of the leg at the knee during the middle of the swinging phase. Fourthly, both erectores spinae contract twice in each step and prevent forward bending of the trunk at the vertebral column.

1. The range of variation in the movements at the metatarso-phalangeal and interphalangeal joints of the big toe in fifty males has been investigated by means of lateral radiographs.

2. In the "neutral" position the proximal phalanx is dorsiflexed on the metatarsal and the distal phalanx dorsiflexed on the proximal. Sometimes the distal phalanx is plantar flexed on the proximal but this is not associated with any obvious abnormality of function.

3. There is a wide variation between individuals in the amount of movement found at these joints.

4. At the metatarso-phalangeal joint dorsiflexion is much more free than plantar flexion. The opposite is the case at the interphalangeal joint.

5. There is no significant difference between the right and left sides. Only in plantar flexion at both joints are there significant reductions in the range of movement in older age groups. These reductions are not functionally important.

6. There is an inverse relationship between active and passive dorsiflexion: the greater the range of active dorsiflexion, the less is the range of additional passive dorsiflexion.

7. In lateral radiographs the head of the metatarsal is always rounded.

1. The range of variation in full extension at the interphalangeal and metacarpo-phalangeal joints of the thumbs of 133 male and 100 female Europeans, and of 31 male Indians and 30 male Africans, has been investigated.

2. There is considerable variation between individuals in the maximum extension of both joints of the right and left thumbs in all groups studied.

3. The distribution for each joint in both thumbs in all groups is fairly symmetrical.

4. There is a high correlation between the right and left thumbs for both joints in all groups

5. The mean angle of extension at the right and left metacarpo-phalangeal joints in all groups is similar. Female Europeans, however, show a significantly greater mean angle than male Europeans.

6. The mean interphalangeal angle of extension in male Europeans is significantly greater than that in female Europeans and the mean in the Indian and African groups is significantly greater than in the male European group.

7. There is slight negative correlation between the metacarpo-phalangeal angle and interphalangeal angle in each thumb in the European groups.

8. Many subjects in all groups can increase extension at the metacarpo-phalangeal joint after flexing the carpo-metacarpal joint. Marked hyperextension (over 40°) is more frequent in the left than in the right thumb, in females than in males, and in male Indians than in male Europeans and Africans.

9. Maximum extension at the interphalangeal joints is not related to the presence of a sesamoid bone in the anterior part of the capsule of the joint.

10. The surfaces of the metacarpo-phalangeal joints vary considerably in shape. Those which are flat form about 10 per cent. of the sample and do not show hyperextension.

11. The factors influencing the amount of extension at the interphalangeal joint is the degree of laxity of the anterior capsule. The problem at the metacarpo-phalangeal joint is more complex; both the capsule and the shape of the joint surfaces play important roles.